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Kathryn Marit Sather 



The Graduate Program in Historic Preservation 

Presented to the faculties of the University of 
Pennsylvania in Partial Fulfillment of the 
Requirements for the Degree of 



Samuel Y. Harris, Lecturer, Historic Preservation 

V^eanne Marie Teutonico, Lecturer, 

Historic Preservation 


^©dvid G. De top^, l^rofess^or of/-^rchi 

Graduate Group Chairman 



/VA 10^ / '^-^'3 / ^7.^ ^ 


To my Bister, Krista 

















I would like to thank my advisor, Samuel Y. Harris 
for his encouragement and knowledgeable advice; Jean 
Marie Teutonico for synthesizing technical and 
theoretical approaches; and all of the other people who 
shared their time and knowledge. 

I also would like to e>;pres5 my gratitude to the 
members of my family and my friends for their constant 
encouragement and support. 



Although the quarrying of granite for use as a 
building and monumental stone dates back to ancient 
civilizations such as Egypt, the actual use was often 
reserved for sculpture and choice locations in temples 
and monuments, including the famous obelisks and veneer 
in a few small rooms in the Temple of Karnak . The 
extreme hardness of granite, as compared with other 
available stones like marble and limestone, precluded 
granite from widespread use as a building stone. With the 
mechanization of the quarry process, the advent of 
pneumatic hammers, and the development of carbide and 
diamond tipped saws, the hardness of granite became less 
of an economic consideration. 

The durability of granite, related to its low 
porosity and non-calcareous mineral structure, made 
granite a popular building material, both as a building 
stone and for monumental and sepulchral uses. Due to the 
relative durability and recent widespread usage in the 
United States, granite deterioration has received little 
attention outside of academic petro logical journals. 
There is a lack of information on tkie mechanisms of 
deterioration and options for intervention available to 
an architectural conservator when faced with a 

deteriorated granite object or building. 

After roughly one hundred years of exposure, it has 
become apparent that granite does in fact deteriorate, 
althoLigh at a slower rate than other corrrmon building 
stones. The superior qualities of granite as a building 
material led to its widespread use for tombstones, 
beginning in the last quarter of the nineteenth century. 
Marble and sandstone tombstones have been used in 
numerous studies as examples of stone weathering. The 
fact that the stones ^^re often placed in direct contact 
with the soil, sre relatively thin, and ^re exposed on 
all sides leads to accelerated weathering as compared 
with building stones which have some measure of 
protection provided by a roof and the surrounding stones. 
For these reasons, this study utilizes granite tombstones 
as examples of stone deterioration. 

The churchyard of St. James the Less, a National 
Landmark located in Philadelphia, contains many granite 
tombstones which exhibit differing types of 
deterioration. The examination of these tombstones and 
the determination of the causes and rates of 
deterioration should help determine the necessity for and 
possible methods of intervention. This case study will 

provide a review of the mechanisms of granite 
deterioration as they apply to gravestones, which when 
coupled with the analysis of the surface deterioration of 
the granite gravestones at Saint James the Less, may be 
applicable to other uses of granite as a building or 
monumental stone. 


(1) Mary Winearls Porter, UJhat Rome Was Bull t With 
(London: Henry Frowde, 1907), 62. 



The weathering characteristics of granite are in 
part determined by the formation process, the properties 
of the mineral constituents, and the methods used in the 
quarrying and dressing processes. An understanding of 
these properties and processes provides a basis for 
understanding the complex interactions between the 
granite and the environment which produce various types 
of surface deterioration on the tombstones. 

All igneous rocks are formed when magma, which is 
molten silica found below the earth's crust, makes its 
way into the earth's crust. If the magma is allowed to 
cool within the crust, the resultant rock is called 
intrusive or plutonic. These rocks are characterized by 
coarse grains, as the magma cools very slowly and large 
crystals are formed. If the magmra is extruded above the 
earth's surface the magma undergoes rapid cooling and the 
resultant grains are much finer. These rocks are called 
extrusive or volcanic. Granite is an intrusive rock that 
is exposed to the surface by the weathering of less 
durable rocks above it and by movements in the earth's 
surface. " 

The coarse-grained or phaneritic texture of granite 
is important, as the larger the grain size, the more the 
minerals will behave according to their individual 
properties.-' The minerals formed in the crystallization 
of an igneous rock depend on the elements present in the 
original magma and upon the changing temperature of the 
magma as it cools. The minerals whxch make up granite 
are chiefly quartz and feldspar. 

Quartz comprises up to 25'/. of granite and is formed 
from silicon and oxygen." It is colorless when pure, but 
impurities can impart a light gray, yellow, pink or 
violet color. It has a glassy appearance and a hardness 
of 7 on the Mohs scale . 

Plagioclase and orthoclase feldspar can constitute 
over 507. of granite. Both types of feldspar have a 
hardness of 6 and form elongated crystals in igneous 
rocks. Plagioclase feldspar forms from aluminum, silicon, 
oxygen, and either sodium or calcium, and varies in color 
from white to gray. Orthoclase feldspar contains 
potassium, aluminum, silicon, and oxygen, ranges in color 
from white to gray but is often a salmon pink color, and 
is much more common in granite than either the sodium- 

rich or calcium-rich plagioclase feldspars 


other minerals present can include either mica in the 
form of muscovite or biotite, and amphibole, usually in 
the form of hornblende. The micas have a hardness of 
between 2-3 on the Mohs scale and can easily split into 

parallel sheets due to a weak bond between the more 

strongly bonded layers. Muscovite ranges from a clear to 

a light gray, green or brown color, and is less common 

than biotite, which is characterized by a black, dark 

green or brown color. Although different in structure, 

both micas contain potassium, aluminum, silicon, 

oxygen, and hydrogen. Biotite also contains magnesium and 

iron as well. ■ Amphibole is a comple;-; family of hydrous 

calcium, sodium, magnesium, iron, and aluminum silicates 

of which hornblende is a common member. The colors range 

from dark green to black and the mineral has a hardness 

of between 5 and 6 on the Mohs scale. •*■ 

Due to the mineral constituents and the process in 
which it is formed, granite e;;hibits properties which 
make it an ideal building and monumental stone. Granite 
has an extremely low porosity, between 0.3 and 1.5"/. .■'••^ 
The bulk density (gm/cm3) is 2.5-2.8.-^-' Granite is also 
very hard due to the hardness of the minerals, and 
commonly has compressive and tensile strengths higher 
than other common building stones. 

Beyond the formation process and mineral properties 
of granite, the quarrying and cutting processes also 
affect the weathering characteristics. Although bronze 
chisels were found in Egyptian quarries, early granite 
quarrying techniques are not well documented. At this 
point in time quarries use a variety of extraction 
methods, the choice of which is somewhat dependent upon 
the relation of the granite mass to the topology of the 
site and the structure of the granite itself." The 
oldest methods depend upon the advantageous manipulation 

of the rock, structure, either on the large scale in the 

1 R 
form of fissures and planes of weakness, or on thie 

particle level using the cleavage planes between the 

minerals. The methods most commonly used in large scale 

quarrying today depend upon the force of explosives and 

the hardness of the materials used to tip the saws. 

The oldest methods used different forms of wedges to 
split off sections of rock. One type of wedge method 
still employed is called plugs and feathers, referring to 
the wedge shaped plugs and the two curved or angled 
guides for each plug. In this method, a linear series of 

holes are drilled in the granite face, usually 6-9" 

1 9 

apart, :.-6" deep and with diameters of an inch or less. 

The metal feathers are inserted in the hole opposite each 


other and the plug is placed in the center. The plugs ArB 
tapped into the granite in succession along the line, 
repeating the tapping process several times, allowing the 
granite to split along the particle cleavage planes, 
producing a flat rough face. 

The introduction of black powder blasting issued in a 
new approach to granite quarrying which relied on extreme 
forces and very hard tipped saws to extract the stone, 
and which characterizes the majority of granite quarrying 
operations today. Low powered blasting using dynamite, 
black powder, ammonium nitrate fuel, and slurries of 
water, fuels and oxidizers btb commonly used in many 
granite quarries, and have drastically increased the 
output of the quarries since their introduction.'"" 
Although used in a variety of situations, in dimension 
stone quarrying the charges can be used to open up 
channels to facilitate removal of large blocks and to 

o 1 

loosen the blocks from the face.'" Compressed air, from 
70 — 100 psi , has also been used in conjunction with 
d'/namite and black powder blasting, and can save time if 
the quarry and rock conditions permit its usage. '^'^ The 
plug and feather inethod is often used in conjunction with 
these other quarrying methods, although using air hammer 
drills. -^^-^ 

Jet flame cutting is another technique which uses a 
flame that moves at five times of the speed of sound and 
burns at 5000F . As the minerals that formed the granite 
have different coefficients of expansion, stresses 
built up internally which cause the heated areas to spall 
off. This technique is used in chanelling, cutting, and 
dressing . 

Another recently developed method utilizes 
continuous belt wire saws which cut by abrasion with the 
additions of sand and water. The cut progresses about two 
inches and hour and can descend 50-7u feet deep."-" 

After the granite has been removed from the rock 
face, saws tipped with either diamond or tungsten carbide 
Bre used to reduce the large blocks into smaller square 
blocks or into slabs.'- 

The finishing techniques and tools used on granite, 
although now mechanized, remain largely unchanged with 
the one exception of the jet flame finish discussed 
earlier. The polishing and dressing processes are now 
automated or at least augmented with compressed air 


Polishing is a process of rubbing the stone surface 
with increasingly fine grades of abrasive until the 
surface is completely smooth and reflects light. Granite 
is a stone which takes a polish extremely well. F'olishing 
machines are now automated, but previously there were 
hand operated rotating-disc polishing machines. These 
machines used a silicon carbide grit in a range of 
grades, the final polishing using a felt pad and tin 
oxide . "" 

Monumental stone relief finishes are not usually 
carved but shot-blasted. A rubber stencil is placed on 
the stone and the whole area is blasted with silicon 
carbide grit. The rubber overlay protects the stone 
underneath 4iiiile the unprotected stone is evenly removed 
by abrasion.'^ 

The tools used for finishing granite have not changed 
much through time, although the order of usage of the 
tools has changed. '^^ Many of the hand finishing tools are 
also directly powered by electric or compressed air 
instead of separate hand held hammers and mallets. The 
cost of the labor intensive methods of hand finishing has 
favored the use of machined finishes, such as polishing, 
grit blasting and sawn blocks. However, traditional 


carving and dressing tools sre still used where special 
surface finishes are required. 

The tools used on granite dressing include chisels, 
bolsters, punches, claw tools, pitchers, and bush 
hammers. The pitchers have wide, flat and thick ends and 
arB used first to remove large pieces of excess stone, 
followed by a punch which is pointed, used for the rough 
shaping. Ne;;t the surface is worked over with a claw tool 
and finished with a variety of chisels and bolsters. The 
bolster has a wide and flat edge and is used for shaping 
and surfacing. The tips of the chisels can be either 
straight, skewed, pointed, or bul 1 nosed . -''-' Bushhammers 
have a head of individual pyramidal points and are widely 
used on granite to produce a fine, level surface finish 
appropriately named after the tool. Most finishing tools 
are now tipped with tungsten carbide or carbon steel. ■-^■'■ 

It is useful to understand the finishing and 
quarrying techniques of granite as they may have created 
conditions in the stone surface which will affect how the 
stone weathers once e>;posed to the environment. 
Information concerning the formation, properties, and 
mineral constituents of granite can also be relevant in 
understanding the different environmental reactions which 
lead to surface deterioration. 



(1) Ehard M. Winkler, Stone : Properties , Durabi 1 ity in 
Man ' s Environment (New York: Sprinqer-Ver lag , 1975), .1-2. 

(2) Richard Nuir, The Stones of Britain (London: Michael 
Joseph, 1986), 12. 

(3) Winkler, Stone , 1 . 

(4) Edward J. Tarbuck and Frederick K. Lutgens, The 
Earth; An Introduction to Physical Geology 3rd ed . 
(Columbus, Ohio: Merrill Publishing Co., 1990), 55-56. 

(5) Tarbuck, 40, 60. 

( 6 ) McGraw-Hi 1 1 Encyc lopedia of Science and Technolog y 
6th ed . , s.v. "guartz." 

The Mohs scale of hardness, developed in 18S2, 

assigns minerals a number between 1 and 10, based upon 

the ability of the mineral to scratch and in turn be 

scratched by other minerals on the scale. 












Orthoc lase 









The scale is not linear but geometric, as each number 
marks a two-fold increase in indentation. The hardness of 
a mineral corresponds to the strength of the weakest 
bonds, thus the van der Waals bonds of talc place it at 1 
and the covalent bonds of diamond place it at 10. 
(Tarbuck, 36; Encycopaedia Bri tannica 15th ed . , s.v. 
"minerals . " ) 

(7) Tarbuck, 60. 

(8) Tarbuck, 43-44. 


(9) McGraw-Hill , s.v. "mica." 

(10) McGraw-Hill , s.v. "mica." 

(11) Winkler, Stone , 197. 

(12) Encyclopaedia Britannica 15th ed . , s.v. "physical 
properties of rocks." 

(13) Encyc lopaedia Britannica 15th ed . , s.v. "physical 
properties of rocks." 

(14) For comparison purposes, selected properties of 
common building stones: 

Density Porosity Compressive Tensile 
(g/cm3) (7.) Strength( psi ) Strength ( psi ) 


Granite 2.5-2.8 0. 

Sandstone 1.9-2.5 5-35 

Limestone 2.5-2.7 0.1-15 

Marble 2.6-2.3 0.4-2 

30 , 000-50 , 000 500-1000 

5 , O O - 1 5 , O C) C> 10 — 2 

2 , O O - 2 O , <I) O 4(1)0-850 

1 5 , <I) O O — 3 O , O O O 7 O O — 1 O O 

Table compiled from: Encyc lopaedia Britannica , s.v. 
"physical properties of rocks"; McGraw— Hi 1 1 Encyc lopedia 
of Sc ience and Technology 6th ed . , s.v. "rock". 

(15) Porter, 59. 

(16) Patrizia Balenci, et al, "Investigation on the 
Degradation of the Stone: XI- Historical Research on the 
Techniques of Working," in Conservation of Stone I I Part 
A, 2nd ed . (Bologna: Centro per la Conservazione delle 
Sculture all' aperto, 1981), 165-194. 

This article provides the most complete source of 
information on historic quarrying and dressing 
techniques . 

(17) A.T. Armstrong, comp., Handbook on Quarrying 4th ed . 
(Government Printer, South Australia, 1933), 121. 

(18) Hugh O'Neill, Stone For Bui Idinq (London: Heinemann , 
1965), 70. 

(19) O'Neill, 70. 

(20) Encyc lopaedia Britannica 15th ed . , s.v. "mxning and 
quarrying . " 


(21) Halbert Powers Gillette, Handbook of Roc k Excavatio n 
Methods and Cost (New York: McGraw-Hill Book Co. Inc., 
1916), 572. 

(22) Gillette, 578-579. 

(23) Gillette, 577. 

(24) O'Neill, 72. 

(25) McGraw-Hil 1 6th ed . , s.v. "quarrying." 

(26) O'Neill, 91. 

(27) O'Neill, 94. 
(23) O'Neill, 95. 

(29) Peter Rockwell, Lecture at ICCROM, Rome, August, 

(30) Richard Grasby, Lettercuttinq in Stone (Oswestry, 
England: Anthony Nelson Ltd., 1939), 24. 

(31) O'Neill, 96. 



The formation process, the properties of the 
specific mineral constituents, and the quarrying and 
cutting processes taken together with the environment in 
which the stone is placed form the mechanisms responsible 
for deterioration. The mechanisms which contribute to the 
deterioration of granite can be grouped into three 
separate categories; mechanical, chemical, and 
biological. In practice, however, deterioration often 
results frcin the interactions of these mechanisms. 

The deterioration of granite due to mechanical 
processes range from weaknesses and stresses formed while 
the magma cooled, to excessive force used in quarrying 
and finishing methods, to salt crysta 1 lation at+cl stresses 
due to thermal expansion. 

As the molten rock which forms granite does not cool 
all in one instant, but very gradually, planes of 
weakness can develop where the minerals are not strongly 
bound together. These btb not like the parallel bedding 
planes of sedimentary rock, but instead tend to be 
irregular. These areas of weak bonds can become evident 
after the stone is cut and dressed. The shocks created in 
blasting and in the percussive blows of finishing can 


serve to further reduce the bonds and create minute 
cracks or fissures. These allow water to ingress and thus 
facilitate other mechanical or chemical deterioration 
mechanisms . 

Winkler describes another process which results in a 
visually similar appearance of thin sheets spalling off 
the face of the stone. ^ Since granite is an intrusive 
rock, the hot magma is forced into voids or cavities 
surrounded by previously formed rocks. Internal stresses 
created in this environment are no longer confined 
internally when the blocks are extracted from the 
surrounding rock structure. The phenomenon of rock bursts 
and sheeting in granite quarries has long been 
acknowledged and is a manifestation of these same 
stresses.-' Again, this process is augmented by other 
stresses on the stone, such as thermal expansion. 

The extent to which dynamite, black powder, and 
other types of blasting cause the degradation of granite 
is unknown, but most sources agree that heavy blasting 
does damage the stone. Minute cracks have been found in 
both marbles and limestones which were extracted by 
blasting. Another source blamed the "shattering effect 
of the dynamite" for the exceedingly poor condition of 
the granite, also stating that granite extracted using 


black powder proved unacceptable as well." The minute 
cracks serve to facilitate chemical deterioration, 
providing the needed space for water infiltration and 
salt crystal lation . Quarrying operations now use low 
powered e;;plosive5 to remove granite, but research on the 
effects of differing blasting charges on granite 
weathering has not been conducted and widely circulated, 
so acceptable blasting levels have not yet been 
determined . 

The effects of finishing techniques on the 
weathering characteristics of marble and sandstone have 
been researched in a series of studies. These reports 
used a variety of methods to evaluate stones worked with 
a bushhammer and with chisels. The studies showed that 
the surfaces worked with the bushihammer were 
overwhelmingly degraded, and that the chisels also caused 
some deterioration, both of these in the form of tiny 
cracks in the finished surface. The applicability of 
these studies to granite may be somewhat limited, as the 
constituent minerals of granite bt^ mostly very hard, and 
thus would resist the crushing and cracking more than the 
marbles and sandstones. 

Salt crystallisation, referred to as salt fretting 


when found on granite, is often named as the culprit of 
the fairly common surface peeling of granite, without 
further proof except for the visual evidence of a thin 
spalling area on the face of the block, Winkler points 
out that this phenomena is also found in areas not 
exposed to water taorne salts. Given the extremely low 
porosity of granite (from 0.5 -1.5"/.) it seems unlikely 
that, salt crystallization can cause a significant amount 
of deterioration, unless the surface of the block was 
sufficiently degraded by tiny fassures, which would 
greatly increase the porosity of the stone along this 
surface . 

The differing coefficients of thermal expansion of 
the minerals in granite is used to advantage in the jet 
flame miethod used in quarrying and finishing. Thermal 
expansion within normal daily temperature ranges is also 
used in quarrying to finish separating granite masses 
after light charges of powder placed m the horizontal 
mass have loosened a lens shaped ArGA. li the 
differences in the expansion of granite minerals is such 
that it can be utilized to separate the rock, it stands 
to reason that these same forces sre sufficiently strong 
to breakup the cut granite stones. 

Geology provides a basis for understanding the 


chemical deterioration of granite in universally accepted 
theories of progenesis. Due to the slow rate with which 
granite weathers, it is helpful to study how granite 
formations ars broken down in the soil forming process. 
Granite deterioration due to a chemical mechanism is 
basically a process of hydrolysis. Most silaceous stones 
are affected by this process to differing degrees, 
depending on their mineral contents. In theory, 
hydrolysis can occur in pure water with the watt-jr 
molecules separating into positively charged hydrogen 
ions and negatively charged hydro;;yl ions. 

H2O > H"^ + HCD~ 

The positively charged ions in the crystalline rock 
structure can be replaced by the hydrogen ions and the 
minerals disintegrate as their internal structure is 
interrupted . 

Most water is slightly acidic due to the formation 
of carbonic acid in thie atmospliere when carbon dioxide 
dissolves in water. 

CO^ + H,,a > H^CO-T 

The carbonic acid separates in water into hydrogen ions 
and bicarbonate ions. 

Most granites contain orthoclase feldsp£Hr, also called 


potaBsium feldspar. The potassium is the element which i; 
attacked in the deterioration process. When water 
containing carbonic acid comes in contact with granite, 
the hydrogen ions replace the potassium ions in the 
feldspar. The end product of this reaction is a clay 
mineral kaolinite. 

2KAlSi-.0o + 2(H"^ + HCO-^ ) + H^O > 

potassium carbonic acid water 


Al^SioO^,(OH)^ + 2K"^ + 2HC0-;r~ + 4Si02 
kaolinite potassium bicarbonate silica 

ion ion 

\ / 

in solution 

As the potassium feldspar decomposes into kaolinite, the 
bonds with the surrounding minerals is released leaving 
the quartz and other minerals as unattached particles, 
thus contributing to the granular dissolution of the 
rock . 

This process can be seen in the feldspar as the 
mineral, which usually has a pearly luster, turns cloudy 
and then into the clay. On a larger scale, this process 
can be seen in huge granite formations where a crevice 
has given water access to the rock surface and the crack 
has become filled with clay This same process is also 

evident where large clay deposits &<r& found above granite 

masses . 


This process of deterioration is a reaction between 
the granite minerals and weakly acidic water. In 
industrial or otherwise polluted environments the rain 
water often contains sulphuric acid and/or nitric acid. 
Both of these acids s^rs considerably stronger than 
carbonic acid and it follows that these acids may be 
responsible for the increased deterioration of granite 
noticed in large cities and other industrial areas. A 
model for this chemical reaction could be proposed which 
is similar to that for carbonic acid. 

Bacteria, fungi, and lichens have all been 
associated with the biodeterioration of stone. Although 
these microorganisms and lower plants can deteriorate 
rock, their presence on a stone does not guarantee that 
they are the cause of the deterioration. Several studies 
have proven that micro-organisms can reduce feldspar and 
other aluminum silicates to kaolin.-'-' The deterioration 
processes due to micro-organisms and lower plants are 
largely chemical reactions, very similar to the chemical 
deterioration processes previously outlined, save for the 
origin and specific types of acids produced. 

The role of the lower plants m the process of 


progenes.iB has long been accepted. Yet the e>;tent to 
which, and the mechanisms with which bacteria, algae, 
fungi, and lichens contribute to the breakup of rock into 
soil forming particles has been debated with different 
theories vying for acceptance. Regardless of th"ie accepted 
theory, the same mechanisms of biodeter ioration present 
on rock outcrops also lead to the deterioration of 
masonry. Thus the process of progenesis becomes a 
conservation issue when the substrate is cut stone. 

The effects of biodeterioration are most noticeable 
on finely carved elements, such as statuary, tombstones, 
or monuments, so these have received the most attention 
and treatment. Biodeterioration is also much more of a 
problem in warm and humid climates. The microbial popula- 
tion is high in moderate semihumid and humid climates and 
even higher in humid tropical regions. Lichiens in 
particular ^atb sensitive to pollutants, and generally do 
not thrive in urban areas. The information on the subject 
generally reflects these parameters and either represents 
large scale situations in humid, unpolluted regions or 
specific locations where the microclimate was conducive 
to microbial growth, with the majority of information 
addressing decorative elements. 

Bacteria are involved in the production of both 

sulphuric and nitric acids. Sulphur-reducing bacteria 
such as Desul f ovibrio desul f uricans turns sulfate into 
hydrogen sulphide. Some strains of another genus of 
bacteria, Thiobac i 1 lus , can o>;idize the hydrogen sulphide 
into sulfuric acid. Nitrifying bacteria and nitrogen 
producing bacteria can work in conjunction to produce 
nitric acid from nitrogen. In the first step, two types 
of bacteria take either atmospheric nitrogen or nitroge- 
nous organic matter and convert it into ammonia. A thj.rd 
type of bacteria can o;;idine the ammonia to produce 
nitric acid. These acids produced by bacteria attack 
granite, specifically the potassium feldspar minerals, 
through the same processes as when the sulphuric and 
nitric acids are present in rain. 

There also exist micro— organisms which can reduce 
and oxidize the iron contained in minerals. The iron 
content of hornblende increases with the acidity of the 

rock, and granite, as one of the most acidic rocks, often 

1 fl 
contains black colored hornblende. Biotite also 

contains iron, and feldspar may have iron present, 

sometimes in the form of hematite as an accessory 

1 ^ 
mineral. All of these minerals may potentially be 

attacked by iron reducing micro-organisms. 

Lichens sire a lower plant form characterised by a 


symbiotic relationship between fungi and either algae or 
bacteria. As the fungal component is responsible for the 
deterioration of the substrate, lichens considered 
here along with other types of fungal growth. Although 
the rock substrates are deteriorated by mechanical and 
chemical mechanisms, the bulk of research addresses the 
chemical processes. 

Deterioration due to fungal and lichen growth on 
masonry surfaces has been widely documented but not well 
understood. A study of lava flows in Hawaii found that 
the depth of weathered material was 71 times greater 
beneath a lichen cover compared to the bare surface.""" 
Conversely, quarried blocks of stone left for 150 years 

O 1 

still exhibit tool marks beneath a lichen cover.'- In 
response to these observations, many theories have been 
offered, but a definitive explanation has not yet 
surfaced. Part of the problem is that as lichens have not 
successfully been cultivated in a laboratory, all re- 
search on the subject has been site specific. Laboratory 
research has been carried out on the fungal partners of 
lichens, which coupled with the field documentation leads 
to a better understanding of the mechanisms of stone 
deterioration due to fungal growth. 


It appears that the deterioration of maBonry from 
lichens and fungi results from the contributions of 
several different mechanisms, both mechanical and 
chemical . 

Although it is generally accepted that mechanical 
action plays a part in the process of masonry 
deterioration due to the growth processes of lower 
plants, there appears to be some confusion over the 
specific mechanisms. Often repeated explanations iire 
based upon assumptions instead of controlled 
observations, there being only a few examples oi actual 
research into the subject. 

Two writers comment that regardless of the other 
chemical or mechanical processes involved, lichen growth 
on masonry should be discouraged as the lichen thallus 
retains water which could be damaging to the stone 
surface. ■^'^ In considering the potential damage it is 
important to note that rain water is naturally slightly 
acidic due to dissolved CO-, which forms a weak carbonic 
acid, in polluted atmospheres other acids form which ^re 
stronger. So if water is retained in the pores and cracks 
by tl"ie fungal hyphae, there could be a damaging effect. 
However, The hyphae cell walls <^rB gelatinous, especially 
those of the medulla and rhizones, which contact the 


stor"ie surface. The lichens do not have any specialized 
method or structures to control water loss. Eioth 
laboratory testing and field observation document that a 
saturated thallus will dry out in a few hours of dry 
weather.-^-' The water content of a lichen reflects the 
amount of water present in the immediate environment, and 
thus the threat of deterioration due to water retention 
is of minor, if any, concern, and the claims to this 
effect Are unfounded. 

Fry studied the effect of drying gelatin on glass, 
gelatin on shale, and lichens on shale. The gelatin and 
the lichens expand when moist and contract when dry. The 
effect of the strong adhesion between the gelatinous 
hyphae and the substrate can break off particles of rock 
when moisture is lost and the hyphae or gelatin 
contracts.^ These rock particles do not appear to be 
chemically altered, and a<re eventually enveloped by the 
lichen thallus, and the process proceeds to the next 

layer of substrate 


As most masonry is porous to a greater or lesser 
extent, the effect of the hyphae which grow inside the 
pores and cracks should be considered as a possible site 
of mechanical deterioration. Hyphae usually do not 
penetrate into the substrate deeper than a few 

millimeters, but hyphae have been recorded at a depth of 
16mm. ^'^ 

Several studies have attributed the deterioration of 
stone, at least partially, to the mechanical penetration 
of the hyphae, but there is no evidence to support this 
assumption, e;;cept for the observation that hyphal cells 
extend longitudinally when moistened, not radially.*- So 
the uptake of water may create enough pressure for the 
hyphae to borrow into the substrate, but no research 
exists to support this theory. One study of lichens which 
grow on silicate rocks determined that the fungal 
rhizoids only penetrate the mica crystals and that the 
fungal hyphae tend to grow in the mica cleavage planes. 
The author attributed this tendency to chemical deterio- 
ration as the bonds between the layers of mica are both 

mechanically and chemically weak bonds. 


Thus the only mechanical process of deterioration 
that can be supported is the process whereby small 
particles of rock are broken off due to the adhesion of 
the hyphae to the substrate and the contraction of the 
gelatinous material in the hyphae as it dries. 

The mycobionts of the lichen produce or"ganic acids 


as byproducts of the metabolism process. These organic 
acids are readily soluble, and Bre ^^^turally occurring 
chelating agents. So, chelation is the weathering process 
resulting from the production of the acids."- Citric acid 
and oxalic acid ^re the two acids most often identified 
as active in solubilizing minerals. 

There s^re differing explanations for the presence of 
oxalates on stones, and this presence has been documented 
as early as 1853 by J. Von Liebigs in Lieb iqs Annals of_ 
Chemistry ■ ~' ' According to some authorities, oxalates 
occur in plants which were used as coloring agents on 
stone, and oxalic acid was also used as a polish for 
marble." Although these applications may account for 
some of the? oxalates found on stones, mono and di-hydrate 
calcium oxalate has been documented on deteriorated stone 
beneath lichen or fungal growth as well as in the thallus 
itself. X— ray diffraction, a scanning electron 
microscope, and a polarizing microscope have been used to 
differentiate the calcium oxalate crystals on various 
stone substrates; marble columns in Venice, a marble 
figure on a church in Florence, a sandstone monument in 


Kiel, Germany, and on the stones at Borobudur, Java.-''^ 

The oxalic acid crystallizes to form oxalates, and 
is usually deposited within the thallus, accumulating 


with the age of the lichen, but generally forming 50"/. of 
the total weight of the dry thai lus . -'-'' The salts 
formed by the extraction of a mineral from the substrate, 
usually calcium, for/rung calcium oxalate, but magnesium, 
copper and manganese also form oxalates. In this process 
the minerals are converted to either siliceous relics or 
non-cystal 1 ine weathering products.'- The deterioration 
is initially visible as a pitting of the mineral surface, 
but the process proceeds until the cohesion of the sur- 

face is lost, 


Citric acid is also produced from the fungal 
component of lichens as well as other fungi. When a 
lichen-forming fungus of a silicate rock was cultured and 
grown with silicate rock forming minerals, the citric 
acid solubilized a high percent of the minerals: up to 
317. Si, 127. Al, 647. Fe, and 597. Mg . Feldspar and quarts 
were the most resistant minerals." Iron and Magnesium 
were most susceptible to fungal attack, and minerals such 
as biotite and hornblende will deteriorate more quickly 
than the quartz and feldspar in granite. 

The chemical weathering of stones due to the growth 
of a lichen thai lus depends upon the type of rock and 
upon the minerals with which it is formed. The organic 
acids produced b/ the mycobiont can remove the minerals 


by a chelating mechanism, leaving an unstable residue 
behind . 

The deterioration of masonry due to lichen and 
fungal growth follows the same processes as the 
biodeterioration of rock in a soil forming process, which 
can be a combination of both mechanical and chemical 
mechanisms. The lichen thallus often envelops pieces of 
the substrate which ^re not chemically altered, but 
mechanically separated by the adhesion and contraction 
properties of the fungal hyphae, and incorporated in the 
thallus by growth and movement due to the wet/dry 
cycling. Chemically altered minerals, often in the form 
of mineral salts, eire also found in the lichen thallus, 
transported there by chelation processes. Organic acids 
produced by the fungal symbiont in lichens and other 
fungi can solubilize biotite, hornblende and feldspar 
crystals. Bacteria and algae also can deteriorate 
granite, as they produce citric, o;;alic, sulphuric, 
nitric and other organic acids which attack certain 
minerals found in granite. 

Damage attributed to the acid production or the 
chelating action of biological growths can appear very 
similar to deterioration caused by the acids present in 

rainwater, or from the wetting of pollutants which are 
deposited dry on the stone surface. Feldspar and mica are 
the two minerals affected by chemical mechanisms due to 
acidic water; feldspar, mica, and hornblende are all 
affected by biochemical deterioration processes. 
Regardless of the provenance of the acidity and the 
minerals attacked, the result is a differential erosion 
of the crystals, making the surface initially pitted and 
then rougher as more crystals are removed by the actions 
of the deterioration miechanisms . Mechanical weakness, in 
the form of cracks, tiny fissures, stresses and weak 
bonds can be due to the formation, quarrying or dressing 
techniques, salt fretting or thermal expansion. Beyond 
the often disfiguring results of spalling, all of these 
mechanisms contribute to an acceleration of both chemical 
and biological deterioration mechanisms by providing 
protection of and access for water and biological growth. 

The majority of information regarding granite 
deterioration comes from a geological background or has 
been adapted from research on other building stones. 
There is a lack of research specifically addressing the 
weathering processes of granite used as a building and 
monumental stone. However deficient, this information 
provides a preliminary basis for identifying evidence and 
understanding field observations. 


(1) Richard Grasby, conversation with author, January 26, 

(2) Erhard Winkler, "The Effect of Residual Stresses in 
Stone", in The Conservation of Stone I I Part A, 2nd ed . 
(Bologna: Centro per la Conservazione delle Sculture all' 
aperto, 1981 ) , 4. 

(3) Winkler, 4. 

(4) R. J. Schaffer, The Weathering of Natura 1 Bui Idinq 
Stones (London: HMSO , 1932), 17-18. 

(5) Halbert Powers Gillette, Handbook of Rock Excavation 
Methods and Cost (New York: hcGraw-Hill Book Co. Inc., 
1916), 578. 

(6) Giovanna Alessandrini , et al., "Investigation on the 
Degradation of Stones: VIII- The Working Effects on the 
Candoglia Marble," in Third International Congress on the 
Deterioration and Preservation of Stones Venice, 1979, 
411-428; Giovanna Alessandrini, et al., "Investigation on 
the Degradation of Stone: X- Effects of Finishing 
Techniques on Sandstone and Marble," Conservation of 
Stone 1 1 Part A, 2nd ed . (Bologna: Centro per la 
Conservazione delle Sculture all' aperto, 1931), 139-164. 

(7) A.E. Grimmer, A Glossary of Historic Masonry 
Deterioration Problems and Preservation Treatments , 
(Washington D.C.: GPO , 1984), 19; Winkler, "Residual 
Stresses" , 4 . 

(8) Winkler, "Residual Stresses", 4-6. 

(9) Gillette, 577. 

(10) Edward J. Tarbuck and Frederick K . Lutgens, The 
Earth : An In troduc tion to Physical Geoqraphv ^ 3rd ed . 
(Columbus, Ohio: Merrill Publishing Co., 1990), 115. 

(11) McGraw-Hi 1 1 Encyc lopedia of Science and Technology , 
5th ed . , s.v. "feldspar." 

(12) Richard Muir, The Stones of Britain (London: Michael 
Joseph, 1986), 13-15; O'Neill, 66. 

(13) F.E.N. Eckhardt, "Microorganisms and Weathering of a 
Sandstone Monument," in Environmental Bioqeochemistry and 
Geomicrobiolog y Vol.2, ed . Wolfgang E. Krumbein, (Ann 
Arbor, Mich.: Ann Arbor Science Publishers, 1973), 633- 

(14) Erhard Winkler, Stone; Properties, Durabi 1 ity in 
Man • s Environment (New York: Springer-Ver lag , 1975), 157. 

(15) G.G. Amoroso and V. Fassina, Stone Decay and 
Conservation , Materials Science Monographs No. 11 
(Amsterdam: Elsevier Science Publishers, 1983), 100-101. 

(16) John W. Simpson and Peter J. Horrobin , The 
Weathering and Performance of Bui Idinq Materials (New 
York: Wi ley-Interscience , 1931), 77. 

(17) Winkler, Stone , 157. 

(18) McGraw-Hil 1 Encyc lopedia of Science and Technology , 
5th ed . , 5. v. hornblende." 

(19) Mc6raw-Hi 1 1 Encyc lopedia of Science and Technolog y , 
5th ed . , s.v. "feldspar." 

(20) David Hawksworth and David Hill, The Lichen-Forming 
Fungi (London: Blackie, 1934), 37. 

(21) Schaffer, 74. 

(22) Winkler, Stone , 156; Schaffer, 74. 

(23) Mason E. Hale Jr., The Biology of Lichens (London: 
Edward Arnold, 1967), 10-13. 

(24) E. Jennie Fry, "A Suggested Explanation of the 
Mechanical Action of Lithophytic Lichens on Rocks 
(Shale)," Annals of Botany , 33 ( 1924 ): 175-196 . 

(25) Fry, 192-193. 

(26) Hawkswoth and Hill, 35. 

(27) O. Salvadori and A. Zitelli, "Monohydrate and 
Dihydrate Calcium Oxalate in Living Lichen Incrustations 
Biodeteriorating Marble Columns of the Basilica of Santa 
Maria Assunta on the Island of Torcello (Venice)," in 
Conservation of Stone I I Part A, 2nd ed . (Bologna: Centre 
per la Conservasione delle Sculture all' aperto, 1981), 
380; W.E. Krumbein and C. Lange, "Decay of Plaster, 
Paintings and Wall Material of the Interior of Buildings 


via Microbial Activity," in Environmental EiioqeochcE'mistrv 
and Geomic rob io logy , Vol.2, Wolfgang E. Krumbein , ed . , 
(Ann Arbor, Mich.: Ann Arbor Science Publishers, 197S), 

(28) E. Bachmann, "The relation between silica lichens 
and their substratum," Berichte der deutschen Botanischen 
Gesel Ischaft 22 ( 1904 ): 101-104 . 

(29) E.B. Schalsa, H. Appelt, and A. Schaltz, "Chelation 
as a weathering mechanism-I. Effect of completing agents 
on the solubilization of iron from minerals and 
granodiori te, " Geochimica et Cosmochimica Acta , 31 
(1967) :5a7. 

(30) Salvadori, 385. 

(31) Unn Plahter and Leif Einar Plahter, "Notes of the 
Deterioration of Donatello's Marble Figure of St. Mark on 
the Church of Orsanmichele in Florence," Studies in 
Conservation , 16 (1971):117. 

(32) Salvadori; Plahter; F.E.N. Eckhardt, "Microorganisms 
and Weathering of a Sandstone Monument," in Environmental 
Bioqeochemistry and Geomicrobioloqy Vol.2, ed . Wolfgang 
E. Krumbein, (Ann Arbor, Mich.: Ann Arbor Science 
Publishers, 1978), 675-686; Siswowiyanto , Samidi, "How to 
Control the Organic Growth on Eiorobudur, Stones After the 
Restoration," in Conservation of Stones I I Part B, 2nd 

ed . (Bologna: Centro per la Conservasione delle Sculture 
all' aperto, 1981), 759-768. 

(33) Salvadori, 384. 

(34) Hawksworth and Hill, 86. 

(35) Schaffer, 74. 

(36) Melvin Silverman and Elaine Munoz , "Fungal Attack on 
Rock: Solubilization and Altered Infared Spectra," 
Science . 169 ( 1970 ): 985-987 . 



The Church of Saint James the Less is located less 
than half of a mile east of the Schuylkill river, 
three and a half miles northwest of the center of 
Philadelphia. The immediately surrounding area contains 
residential neighborhoods, several large cemeteries, 
scattered industrial plants, and is near portions of 
Fairmount Park. The churchyard itself is roughly 
triangular in shape, with the ends of the church facing 
east and west. The gravestones of the churchyard surround 
the church building and Are situated in lines parallel to 
the east/west facing walls of the church, so that the 
front face of the upright stones face east. There aire 
approximately 1600 gravestones in the churchyard, of 
which 980 cut from granite or granitic stones. Many 
of the granite gravestones aire from relatively recent 
dates, and the earlier granite stones tend to be 
unpolished and of simpler design as compared with the 
later stones. There is a wide variety of stone types and 
designs within the granite tombstones, ranging from 
medium to coarse-grained, flat tablets to upright 
positioned markers, from simple designs to stones with 
intricate carvings. The oldest granite stone dates from 
1864 and the most recent from 1989. 


In order to facilitate the recording of data from 
the examinations of the gravestones, a granite tombstone 
inventory sheet was developed (Figure 1). Information 
necessary to identify, locate, and date the stone is 
included along with other types of information. Factors 
relevant to mechanisms of deterioration are included in 
the inventory based upon background research and 
preliminary field surveys. This information includes 
factors which affect the weathering characteristics of 
granite, factors which may augment environmental 
influences, and visible evidence of deterioration. 

Beyond factors such as grain size and mineral 
constituents discussed in the chapter on deterioration 
mechanisms, there s^re other factors which affect the 
weathering of granite gravestones. The length of time of 
exposure of a gravestone is important in determining 
rates of deterioration, and the date of death is 
generally considered to be accurate within two years of 
the date of installation of the headstone.-^ The 
orientation of the faces of upright stones affects the 
extent to which environmental factors play a role: heat 
from sunshine, biological growth, abrasive winds all 
affect the stones unevenly. The design of the monument 
also affects the patterns of weathering; horizontal Areas 

Figure 1: Granite Tombstone Inventory Sheet (Sample) 


Sample #_ 

Date of Death 

Appro;;. Years of Exposure 
Lot # or Appro;-!. Location_ 
Design of the Monument 

Orientation of Upright Stones 
Surface Discoloration 

Minerals (color and abundance): 

Quartz Feldspar 

Mica Hornblende 

Grain Size: Coarse Medium 

Visible Biological Growth^ 

Stone Condition: 
Horizontal Areas 

Vertical Areas(SWNE) 

Polished Areas 

Unpolished Area! 



retain water for longer periods, and decorative reliefs 
can guide large amounts of water along the recesses. 
Although there other explanations, green or black 
surface discolorations on granite may be due to 
biological growth, and should be noted. The 
differentiation between horizontal and vertical areas, 
and polished and unpolished surfaces, follows from an 
initial survey which documented differences in the 
surface conditions of these different areas on the same 
stones. Distinction between orientations of the vertical 
faces will also be noted in the documentation of the 
surface condition of the stone. 

The choice of gravestones which would provide a 
representative sample for the purposes of this study took 
into account both age and granite type. The range of ages 
includes recent stones for comparison but depends more on 
stones in the older age categories. Gravestones were also 
chosen for examination to document a range of grain sizes 
and differences in the appearance or relative abundance 
of the mineral constituents. 

The methodology of the gravestone examination 
process first involves recording the information 
regarding identification, date and location as well as 


other factors such as design, orientation and 
discoloration. The remaining information is gained on the 
microscopic level. The stone surfaces Are examined with a 
20>; magnifying lens, and then documented photographically 
with a macro 10;-; lens on black and white film. These 
observations 3.rB made to determine the presence of 
minerals, the size of grains, and the presence of 
biological growths. 

The minerals arB identified by visual properties of 
color, luster, and structure of the crystal formations. 
Grain size is decided on a comparative basis, for 
although granite is characterized by a coarse-grained 
structure, there exists a range of grain sizes within the 
coarse-grained classification. In medium-grained stones, 
the crystals are visible with the magnifying lens and the 
mean grain size is between 1 and 5 mm. In coarse-grained 
stones all of the mineral crystals are visible with the 
unaided eye; mean grain size is greater than 5 mm . -^ 

Visible biological growth is determined by the 
existence of green, red, or black, spherical, globular, 
or strand-like particles, which are usually visible with 
an unaided eye or the strength of the 20>; magnifying 
lens. As the differentiation of biological matter is 
largely aided by color differences, the photographs do 
not adequately document these growths. 


The illustrations referred to in the te;;t Brs in 
Appendix A. The individual inventory sheets are collected 
in Appendix B. 

Thirty granite tombstones were closely examined. 
These headstones ranged from 11 to 127 years of exposure, 
with a myriad of designs and locations within the 
graveyard. The front face of all the upright stones faced 
east . 

The surface discolorations visible with an unaided 
eye varied between green and black. The green areas 
commonly occurred near the ground, on the north side, 
and on the north ends of the east and west sides of the 
monuments. Upon examination under magnification, the 
green areas appeared either globular or more elongated. 
Differing types of black discoloration were observed, one 
type which did not appear to be biological consisted of a 
thin irregular covering which did not scrape away. Other 
black areas were quite thick and always found in areas 
inaccessible to water washing. Another type of black 
discoloration w£-i5 actually green under magnification. The 
fourth type of black discoloration always had pitting of 
the surface associated with it. These surfaces were 


usually located on diagonal areas, such as the angle from 
the base to the body of an upright stone, or on 
horizontal areas. These surfaces were almost uniformly 
darkened except for the pitted areas (illustrations 1-4). 
A distinct type of black discoloration occurred in four 
stones along the edges of polished surfaces 
(illustrations 5 ?< 6). 

Surface deterioration is initially more visually 
apparent on coarse— grained than on the medium-grained 
granites, and also more apparent on polished areas than 
on unpolished sawn finishes and rough dressed stones. The 
horizontal surfaces of unpolished medium-grained granites 
had often lost most of the marks of the sawn finish on 
about a half of the stones that originally had this 
finishing. On these stones the saw marks were still 
visible on the vertical areas (illustrations 7 & 8). Upon 
examination under magnification, it is apparent that the 
uripolished areas Bre more uniformly deteriorated, whereas 
the polished areas may have disfiguring pitting on an 
otherwise unaltered surface. This type of surface 
deterioration can be seen in the absence of the feldspar 
and mica crystals which are distinguishable in the 
polished surfaces (illustrations 9 &. 10). The finer- 
grained granites mask the deterioration effects better as 
the crystals ars smaller and less apparent when reduced 


or lost. 

One tombstone had large areas of the surface flaking 
off. The coloring of the surface of this area of the 
stone varied slightly from that of the rest of the stone 
(illustration 11). The flakes had a relatively even 
thickness and there were no signs of clay. Under 
magnification, an amber colored mineral, probably 
feldspar, appeared unaltered. None of the mineral 
crystals showed any evidence of alteration, the flaking 
appeared to split along the mineral boundaries 
(illustration 12). 

The surfaces of the gravestones were examined under 
magnification to locate and characterize any biological 
growth. Beyond the obvious north side, green growths were 
found on other vertical, diagonal and horizontal 
surfaces, and on polished, unpolished and rough dressed 
areas . 

On the north sides of the unpolished areas, the 
green growth was recorded growing on all of the minerals. 
At other orientations and on horizontal surfaces, a 
biological growth occurred almost exclusively on the 
hornblende. With an unaided eye, where the hornblende 

appeared in smaller crystals, many of the surfaces with 
these growths had a black tinge. In granites with larger 
crystals, the hornblende had a distinct green color due 
to the concentration of the biological growths. Spherical 
green biological growths were also located in the 
recessed areas on all orientations and horizontal 
surfaces of rough dressed gravestones. 

On polished surfaces, different types of biological 
growth were visible. Both green and reddish-orange 
strand-like elongated growths were observed along the 
grain boundaries, and greenish-black growths also were 
located on the polished surfaces of these coarse-grained 
stones . 

The green and red elongated biological growths were 
also visible under the polished surface; the stones where 
these growths occurred were coarse-grained, and were 
documented on recent tombstones only exposed 13 years as 
well as on stones almost 100 years old. In the oldest 
stones there were areas which protruded from the polished 
surface. Along the edges of these areas the quarts 
crystals were chipped and flaked, and the green and red 
growths were visible underneath (illustrations 13 A:14). 

A lichen, or lichenised fungi, was documented on 



stone with almost 100 years of exposure, about one inch 
in diameter. Quartz crystal flakes were attached along 
the edges of the plant, separated from the stone surface, 
and there was an indentation of the stone surface beneath 
the growth. Clay particles were found under the growth 
(illustrations 15 & 16). 

The quartz crystals were the most unaltered, on 
polished areas the crystals retained the smooth surface 
and typical glassy luster; on unpolished areas the quartz 
crystals remained in place, along with hornblende, where 
the other minerals had deteriorated and disappeared 
(illustrations 9 &. 10). 

In all of the gravestones studied, the mica crystals 
were relatively small particles, in all cases smaller 
than the hornblende particles. One fifth of the stones 
apparently did not contain mica. Under magnification, 
mica was often visible in polished areas and on vertical 
faces, but absent on the horizontal and unpolished 
surfaces . 

The hornblende particles had a matte quality similar 
to charcoal. On polished areas the hornblende often broke 
the smooth surface with small pits, appearing as a 

roughening of the crystal surfaces. On unpolished areas 
the particles appeared the same, but were usually the 
only mineral remaining with the quarts on deteriorated 
surfaces (illustrations 1-4, 9). 

The feldspar minerals appeared most often in the 
common salmon pink color, but one third of the stones 
contained amber, light yellow, or a cloudy white 
feldspar. Even in the most recent gravestones the 
potassium feldspar exhibited early signs of 
deterioration. Yet most of the feldspar crystals were in 
excellent condition, the characteristic color and pearly 
luster still intact, on polished, unpolished, and rough 
dressed stones. Often the amber, yellow, and white 
feldspars were found in stones which were in better 
condition than the pink colored feldspar containing 
stones. In the stones exposed over 50 years, some of the 
potassium feldspar crystals were either entirely missing, 
deteriorated into clay, or showed signs of deterioration 
as the crystals became cloudy and clay-like. 

On the horizontal unpolished surfaces of the finer- 
grained granite stones, the feldspar minerals were almost 
entirely absent, whereas some of the feldspar crystals 
were still visible on the vertical faces or on polished 
surfaces (illustrations 9 &. 10). On polished surfaces, 


even those exposed over 100 years, many of the feldspar 
crystals were still smooth, even with the polished plane, 
and still retained the pearly luster, while on the same 
surface in close proximity, there were clay deposits and 
empty holes, presumably where a feldspar crystal 
previously existed (illustrations 17 - 21). 

The summary of the data collected from examining the 
granite gravestones at Saint James the Less follows the 
format of the survey sheet. The analysis of this 
information addresses the general types of evidence of 
deterioration and determines the causes and rates of 
weathering . 



(1) Johannes J. Feddema, Air Pol lution Effects on Marble 
Weathering in Phi 1 adel phia , Pennsylvania (Center ton, NJ : 
C. W . Thormwaith Associates, 1986), 4. 

(2) Richard Thorpe and Geoff Brown, The Field Description 
of Igneous Rocks (Milton Keynes, England: Open University 
Press, 1985), 32. 



Based upon the data gathered on the surface 
deterioration of the granite tombstones in the churchyard 
of Saint James the Less, and the previous research on 
granite properties and deterioration mechanisms, an 
analysis and interpretation can be made to determine 
probable causes, initiating factors, and rates of the 
deterioration process. The majority of information gained 
in the tombstone survey is based upon qualitative 
assessments, and not quantitative measurements, but as 
many of the deterioration mechanisms can be identified, 
at least initially, by visual evidence, the observations 
gained through the tombstone examination surveys provide 
important indicators of the causes of the surface 
deterioration . 

The data indicated several factors which affect the 
deterioration processes which were not addressed in any 
of the relevant conservation literature consulted. 
Following a discussion of these topics, the specific 
observations of evidence of deterioration is analyzed 
using relevant information gathered at the site and 
background information from geological and conservation 
studies. Consideration is given to other studies which 
determined weathering rates of granite, and the 


conclusions Are compared with the conclusions of the 
analysis of the site observations to determine the causes 
and rates of weathering. 

One repeated observation in gathering information on 
the surface conditions of the granite stones is the 
marked difference of surface conditions between polished 
and unpolished areas. Although no research has been 
located to corroborate this observation, the process of 
polishing must create surface conditions very different 
from the unpolished areas, and appears to provide a 
measure of protection to the stone. The explanation for 
this is relatively straightforward; the polishing process 
creates a smooth planar surface eliminating much of the 
rough surface which can harbor algae, collect and hold 
water. Thus the polished areas provide protection against 
both chemical and biological deterioration processes as 
the smooth surface limits both the amount of biologicail 
agents which can adhere to it and lessons the length of 
time of contact with water which can contain carbonic, 
sulphuric, and nitric acids. The presence of polished 
surfaces affects the influence of both chemical and 
biological mechanisms of deterioration of granite. 

Many types of biological growth were documented, but 


only in a few cases can the deterioration be directly 
linked with the presence of the growth; the ingress of 
water can precede, or augment the action of the 
biological growths which cause the degradation of the 
surface. These cases sire examined along with the other 
cases in which biological growth was recorded on the 
tombstones, but there was no evidence of deterioration 
which could directly related to the growths. 

Algae prefers to grow in moist and shaded 
environments, and needs a suitable substrate as it does 
not have highly effective means of attaching to a 
surface, for this reason algae is often the photobiont of 
lichens as the fungal component provides the necessary 
structure. At the graveyard of Saint James the Less, the 
algae was found on all sides of the monuments, with the 
majority on the north side. The algae grew on both 
horizontal and vertical surfaces, but was not found on 
any of the polished vertical surfaces, probably due to 
the fact that the planar surfaces do not provide any 
BrssiB which could harbor the algae. 

Another field observation, while not proof of 
deterioration, is interesting to note. On unpolished 
areas minerals had disappeared, the hornblende often was 
covered with a green biological growth, while the quartz 


crystals were relatively free from growth. A possible 
explanation for this occurrence is the existence of 
certain micro-organisms which reduce and oxidize the iron 
which is present in minerals, including hornblende. The 
hornblende does not appear to be significantly 
deteriorated by the presence of the growth. 

The polished surfaces of several coarse-grained 
monuments, both of recent and lengthy exposure displayed 
strand-like green and red growths between the crystal 
boundaries. Under magnification, these growths appeared 
gelatinous, resembling the descriptions of fungal hyphae. 
These growths were also found in areas underneath the 
polished surface. In these areas the surface protruded, 
had cracks between the crystals, and the mineral crystals 
around the edges were flaked and chipped. Giorgio Jorr sea 
described a similar occurrence in Italy where micro- 
organisms were found growing beneath the glazing of 
tiles, where the glaze was translucent enough to permit 
light through to the growths.'^ It was not clear if the 
micro-organisms were responsible for any deterioration of 
the glazing or were just taking advantage of a protective 
shelter. In the granite stones in question, the quartz is 
translucent enough to transmit light, and the cracks 
could collect water and provide shelter, but the presence 


of the quartz flakes, and relatively unaltered feldspar 
crystals indicates that the mechanism may not be solely 
chemical but possibly also biochemical and biomechanical . 

Out of the thirty gravestones examined, only one 
lichen or lichenized fungi was found. The one recorded 
was appro;!imately one inch in diameter, and as lichens 
grow radially an estimated 0.5- 5.0mm a year,-' this lower 
plant could be from 5 to 50 years old. Flakes of quartz 
surrounded and were attached along the outer edges of the 
lichen. Clay particles cover the area underneath the 
1 ichen . 

The quartz flakes Bre significant, as the chemical 
deterioration processes are not described as having any 
effect on quartz crystals. There are certain bacteria, 
fungi and other micro-organisms which can dissolve 
silicates, but most stuidies on the subject show that 
other minerals are solubilized in much larger 
percentages. One study suggested that the fungal 
component of lichens can break off flakes of stone by the 
mechanical action of the gelatinous hyphae which adhere 
to the stone surface, and when they dry and shrink, can 
separate flakes of shale. Granite does not have the 
parallel layers and fine-grained structure of shale, but 
the same mechanism could be responsible for the quartz 

flakes here, and as the stone in question has been 
exposed for 95 years, it is possible that the surface was 
partially degraded in that area, before the lichen started 
growing, thus weakening the minerals. So in this case it 
seems probable that the damage surrounding the lichen 
could be partly attributed to the mechanical action of 
the plant, and partly to a biochemical process which 
produces the clay. 

Some of the torribstones had other types of 
indeterminate biological growth, which appears to cause 
some minerals to deteriorate. Underneath this growth, on 
a polished surface, certain minerals were pitted and 
stained brown. Several sources also document pitting on 
granite surfaces due to biological growth, or in areas of 
very little atmospheric pollution." Due to the production 
of organic acids and the conversion and reduction of 
minerals by micro-organisms, coupled with documentation 
of this condition in other studies, the deterioration in 
this case seems to be caused by the presence of the 
biological growth on the stone surface. 

The background research on the chemical 
deterioration mechanisms indicated that the potassium 
feldspar crystals would degrade into kaolinite, a clay. 


due to the carbonic, sulphuric or nitric acids in the 
rainwater. The information gained in the tombstone 
examinations confirmed this prediction, but the survey 
gathered other information which was not adequately 
addressed in previous studies. 

In several recent stones which were e;;posed only 11 
and 28 years, the orthoclase feldspars had brick-red 
spots in the centers of the crystals, which appeared like 
stains around a central spot. This condition was found on 
only two stones in the graveyard. One possible 
explanation for this observation os that the feldspar can 
have small amounts of an iron containing mineral, 
hematite, contained in the crystal which turn pink, 
orange, or brick-red when altered chemically. So these 
spots Are the first visible sign of either chemical or 
biochemical deterioration of the feldspar crystals in 
these gravestones. 

The most visible evidence of chemical deterioration 
can be seen on the polished areas where the feldspar 
minerals are often entirely missing so that the surface 
has deep pitting, or the feldspar has deteriorated into 
clay, which is held in place by the surrounding minerals. 
Even on polished granite tombstones around 100 years old, 
only about 5 or 10"/. of the feldspar crystals btb altered. 


On unpolished stones over 50 years old the feldspar can 
be seen on the vertical faces, but not on the horizontal 
areas. Although no research has been located to 
corroborate this explanation, the difference in condition 
between the vertical and horizontal surfaces may be due 
to the amount of contact between the stone surface and 
water, the horizontal, unpolished areas tending to harbor 
the water, thus exposing the stone to longer contact with 
acids present in the water. 

Another observation related to contact with water is 
the areas of a black surface discoloration and pitting 
usually located in areas that receive large amounts of 
runoff, such as the recessed areas in elaborate designs 
and the area connecting the base to the headstone. Upon 
examination under magnification, the white, pitted areas 
Are bright, clean quartz crystals, and the darkened areas 
appear to be a thin film which is not biological and 
which covers all of the minerals. This is a situation of 
differential removal of the minerals, but no evidence of 
clay, or biological growth appeared, so the cause is 
difficult to assign to a particular mechanism, other than 
chemical deterioration. 

There were some observations made in the survey of 


the tombstones which are neither evidence of 
deterioration, nor factors in the process, but which 
deserve an explanation and comment. A type of black 
surface discoloration is common on the upright and 
elaborate horizontal gravestones. These areas ar(^ 
characterised by an even opaque coating and Bre located 
in areas which are inaccessible to water. A similar 
condition has been explained on a carbonaceous stone as a 
deposit of dust which is not chemically of physically 
bonded to the stone and has not altered the stone 

substrate, and is typically located in areas where 

rainwater cannot wash the surface. Condensation is still 

a consideration here, for airborne pollutants can be 

deposited dry on stone surfaces, and then wetted by 

condensation which can react with the pollutant to 

produce acids. There also is the possibility that the 

pollLitants can chemically bond with the stone surface, 

making removal difficult. However, there was no visible 

deterioration associated with this condition on the 

stones examined. 

There arB a few overall observations which can be 
made from this study about the processes and rates of the 
various deterioration mechanisms which affect granite. It 
appears that micro-organisms grow on the tombstones soon 
after their placement in the churchyard, and evidence of 


deterioration due to biological growth has been found on 
stones exposed only 20 years. The process of chemical 
deterioration takes longer before it becomes visually 
apparent, but some stones exposed 11 and 18 years show 
initial signs of weathering. It is difficult to establish 
a rate of deterioration for mechanical mechanisms as 
either the damage is already in place before the stone is 
exposed to the environment, or the mechanisms work in 
conjunction with chemical and biological mechanisms. 

There have only been a few studies which aimed at 
estimating a rate of deterioration of granite. Although 
this study did not generate quantitative measurements of 
deterioration, consideration of these other studies 
yields some information important and relevant to this 
study . 

In 1880, Professor Archibald Geikie presented a 
paper entitled "Rock-Weathering, as illustrated in 
Edinburgh Churchyards" to the Royal Society of Edinburgh 
in which he refers to experiments made by a Professor 
Pfaff of Erlangen which estimated the annual rate of loss 
of material to be 0.0076mm on unpolished and O.OOaSmm 
from polished granite. ° Geikie remarks that the 
experimental stone pieces were left to weather only three 


years which was not long enough to allow true rates of 
disintegration to be measured. Gexkie further wrote: 

Granite has been employed for too short a 
time as a monumental stone in our cemeteries 
to afford any ready means of measuring even 
appro;;imately its rate of weathering. Traces 
of decay in some of its feldspar crystals may 
be detected, yet in no case that I have seen 
is the decay of a polished granite surface 
sensibly apparent after e;;posure for fifteen 
or twenty years. "* 

This observation supports the observation of this study 
that the chemical alteration of the feldspars into clay 
takes to roughily 20 years before becoming visually 
apparent . 

Another study of tombstones weathering rated stones 
over 100 years old on a scale of 1 to 6 depending on the 
readability of the letters, 1 being unweathered and 6, 
extremely weathered. Corrected to an average 100 years, 
granite had an average degree of 1.33. As this 
weathering rate is a qualitative judgment, and not a 
measurement, it cannot be compared with Geikies rates. 
However, Rahn ' s general remarks sre useful reference; 

What little weathering occurred appeared 
to be the pitting developed in biotite and pyroxene 
minerals, particularly on the rough textured 
(unpolished) granite. The polished granite had 
virtually no evidence of weathering; saw marks were 
still visible on tombstones over 100 years old.""^"^ 


It should be noted that the cemetery used in this study 
is located in a rural setting with very little pollution 
in the surrounding Bres, so the granite weathered better 
than in the urban setting of Philadelphia. The saw marks 
on unpolished granite tombstones at Saint James the Less 
were often only visible on the vertical faces; the 
horizontal sur faces were deteriorated enough to obscure 
or remove the sawn finish. The feldspar minerals with 
similar years of exposure were weathered in the 
Philadelphia cemetery and unweathered in the environment 
of rural Connecticut. Geikie's conclusions reinforce this 
observation as the feldspar minerals were deteriorated in 
the polluted environment of late nineteenth century 
Edinburgh. -' These observations indicate that a polluted 
environment, which contributes to an acidic rainfall, is 
a major factor in the deterioration of granite. The ease 
with which micro-organisms and lower plants can establish 
growth on the granite surface also is a factor in the 
weathering of the stones. The determination and 
understanding of the mechanisms responsible for the 
deterioration of granite provides the framework for the 
consideration of appropriate methods of intervention 
which aim to prevent further damage and perhaps to repair 
the deterioration. 



(1) Erhard Winkler, Stone: Propertie s.^ Durabiii.tY in 
Mar's E nvironment (New York: Springer-Ver 1 ag , 1975), 157. 

(2) Giorgio Torraca, Lecture at ICCROM, Rome, August, 

(3) David Hawksworth and Francis Rose, Lichens as 
Pol lution Monitors (London: Edward Arnold, 1976), 5. 

(4) Melvin Silverman and H. Ehrlich, "Microbial Formation 
and Degradation of Minerals," Advances in Microbiolog y 6 

( 1964) : 153-206; Winkler, Stone , 155-158. 

(■=.) Ian Wainwright, "Lichen Removal From an Engraved 
Memorial to Walt Whitman," APT Bull etin 28, no. 4 (1986): 
46-51; Perry H. Rahn , "The Weathering of Tombstones and 
its Relationship to the Topography of New England," 
Journal of Geological Education 19 ( 1971 ): 112-118 . 

(6) Mc Graw-Hill Encyclopedi a of Science and Technology 
6th ed., s.v. "feldspar." 

(7) Dario Camuffo, "Wetting, Deterioration and Visual 
Features of Stone Surfaces in an Urban Area," Atni05E.!jeric 
Environment 16, no. 9 (1982):2255, 2253. 

(8) Archibald Geikie, "Rock-Weathering as Illustrated in 
Edinburgh Churchyards," Proceedings oi the Royal Society 
of Edinburgh , (1330): 531. 

(9) Geikie, 513. 

(10) Geikie, 531. 

(11) Rahn, 112-113. 

For comparison, the degree of weathering of 
sandstone was 2.92; marble, 2.82; and schist, 2.47. 

(12) Rahn, 114. 

Rahn may have confused pyroxene with hornblende as 
the visual characteristics arB similar. In the rock 
forming process, under certain environmental conditions, 
formerly crystallized hornblende becomes unstable and 
breaks down, forming pyro;:ene (McGraw-Hi 1 1 , s.v. 
"hornblende"). Granite and granodiorite usually contain 
amphibole, of which hornblende is a member, and pyroxene 


is found in more basic rocks such as diorite, gabbro, and 
pendotite (Richard Thorpe and Geoff Brown, Ihe Field 
Description of Igneous Rocks , [Milton Keynes, England: 
Open University Press, 1935], 43. 

(13) Giekie, 519, 531. 


After the deterioration of an object has been 
documented and the mechanisms identified, it is 
appropriate to consider if suitable interventions exist 
which will halt or retard the deterioration processes. 
The first option is to choose not to intervene, to do 
nothing. This can be an appropriate choice when available 
treatments fail to meet standards of reversibility or 
retreatment, or s^re otherwise inappropriate. The second 
option IS to accelerate the rate of deterioration, as is 
the case in controlled demolition when considerations of 
public safety preclude preservation concerns. However, 
this is a ra^re occurrence. The third option is to 
intervene in the process of deterioration. 

A model has been proposed which separates the 
differing factors of deterioration and suggests 
approaches for intervention which address these 
individual components (Figure 2). In this model a 
deterioration mechanism results from the interactions 
between the material and the environmental factors. The 
options for intervention can be grouped into three 
approaches based upon the specific component of the 
deterioration model they address. 


Deterioration : 

Material + Environment > Mechanism 

Intervention: •'^ '^ ■'^ 

Reconstitution Mitigation Circumvention 

Figure 2: Intervention Model 

Reconstitution involves an alteration to the 
material; replacement, repointing, and reconstruction 
fall into this category. As the environment remains 
unchanged, the deterioration process will continue as 
before, affecting the new material. Mitigation addresses 
the environment wxthout intervening in the material, and 
works to slow the rate of deterioration. Circumventidn 
seeks to alter the set of necessary and sufficient 
conditions which give rise to the deterioration 
mechanism. This approach receives the most attention in 
the form of technological research and experimentation. 
This approach often introduces another material in the 
treatment process and effectively substitutes the 
deterioration mechanism of the original material for a 
different mechanism of the new material. If the 
mechanisms affecting the new material arst understood, 
expected, and preferable to those of the original 
material, and if the treatment meets standards of 


reversibility or retreatment, then the treatment may be 
an appropriate intervention. 

If the deterioration is due to biological action, 
the model is as follows: the material here is granite, 
the environment is the presence of biological organisms 
plus water, and the mechanism produced is biochemical 
dissolution. There atb at least three approaches for 
intervention . 

The reconsti tution approach suggests recuttinq the 
stone, which is a common practice in some cemeteries on 
marble gravestones where the name of the deceased or the 
design of the monument is deemed to be more important 
than the original remaining stone surface. This approach 
results in the loss of original design as any new work 
erases all traces of the old stoneworking techniques, and 
irreversibly alters the monument. An underlying belief to 
this approach is the idea that objects should look new 
and clean, and that it is undesirable to show the 
weathering of time. International charters which address 
the preservation of cultural property stress the 
preservation of original material, and the preservation 
of a materials patina, or the visible signs of age which 
develop over time. Based upon these charters, and 
prevailing preservation theory, the recutting of 


weathered monuments is an undesirable option that serves 
to damage the significance of the monument. 

Approaches which aim to mitigate the environmental 
influences^ limited to repeated treatments with a 
biocide appropriate to the organism. There are a 
variety of algicides, fungicides, and general biocides 
available, but continued treatments are necessary as 
growth will reoccur as soon as conditions permit. 

The final approach of circumvention aims to block 
the organisms, and the water they need, from access to 
the stone material. Waterproof and water-repellent 
coatings, and these coatings with biocide additives, 
serve to form tJiis barrier. Waterproof coatings have 
fallen from grace as they serve to block all water and 
can create more damage than they prevent as water may 
enter from another route and cannot esc^tpe. Water- 
repellent coatings allow the passage of water vapor, but 
repel liquid water. The inclusion of a biocide serves to 
strengthen the power of the treatment against biological 
agents of deterioration. 

Another option that circumvents the biological 
mechanism is the removal of the gravestone from the 


environment and possibly includes the replacement with a 
replica. This approach is also practiced but the practice 
is not generally recommended as the gravestone loses some 
of its integrity when removed from the context of a 
cemetery . '^ 

If the deterioration of granite gravestones is due to 
the action of acidic rain water, the options for 
intervention Bre similar to those outlined above. Again 
the gravestone can be recut but this is not an 
appropriate alternative. An option in mitigating the 
effects of the environment is to lower the amount of 
pollution in the atmosphere, a long term solution 
perhaps, but also an effective approach on a global scale 
as it does not alter the monument. The importance of this 
approach has been voiced by many international 
conservation organizations and individual conservators. 

The circumvention options again offer a coating, 
preferably a water-repellent coating vjhich is impervious 
to the action of the acids present in the ram water. 

Some marble gravestones have been removed to 
interior environments to stop the deterioration process, 
but again, this option is a drastic measure which alters 
the context and significance of the monument. 


The intervention proposals based upon a model of 
deterioration mechanisms and aim to interrupt the process 
of deterioration. Choices for intervention should 
consider the amount of surface deterioration and the 
significance of the monument as well as the reversibility 
or retreatabi 1 1 ty of the proposed treatment. 



(1) The model used here to identify intervention options 
was developed by Samuel Y. Harris, and discussion of the 
model draws upon class lectures on the subject. 

(2) For a discussion of this subject see; 

Robert P. Emlen, "Protective Custody: The Museum's 
Responsibility for Gravestones," in Markers 1 (1979/30) • 



Information on the mechanisms of granite 
deterioration and appropriate interventions is not 
readily available to architectural conservators. This 
information has been gathered from sources on geology and 
from conservation literature pertaining to granite as 
well as other building stones. An understanding of the 
formation processes of granite, the properties of the 
mineral constituents, and the working techniques provides 
a basis for understanding the various mechanisms of 
deterioration and the complex interactions which produce 
the surface deterioration. 

It should be stressed that there are many factors 
which affect the weathering characteristics of granite 
which have not been adequately researched. There btb also 
only a few published cases of treatments to granite, such 
as Cleopatra's Needle in New York City. Even well known 
cases such as this obelisk have caused disagreement among 
e;;perts as to the cause of the surface deterioration. 
Hopefully, more research will be conducted in the future 
to provide a better understanding of the mechanisms 
responsible for the surface deterioration of granite. 

The approach for examining the granite tombstones 


developed in this study assumes a familiarity with the 
mechanical, chemical, and biological mechanisms of 
deterioration and the visual evidence of these processes. 
The examination process is based upon a visual inspection 
and requires only a high powered misgnifying lens. This 
approach is simple, and readily available as a tool for 
field diagnoses. Knowledge of the materials, 
deterioration mechanisms, and treatment options of 
granite will enable archi tec tur^^l conservators to make 
appropriate decisions regarding the treatments of granite 
monuments and buildings in an effort to preserve part of 
a CLiltural heritage. 





























' ^.f rv 






' 1 




^'-.*» » 






... - ■ ■ - -. 








Sample tt 1_ 

Name Susan wife of Geoi-Qe Hi rneison Sr. 
Date of Death harch 18, 1B64 

Appro;;. Years of Exposure 126 

Lot tt or Approx. Location 273, 

Design of the Monument vert cross on vau lt base 

Orientation of Upright Stones E 

Surface ni c;rr.1 oration dark on unwash e d ar ea5_,__no. gjieen 

Minerals (appearance and color): 

Quartz XX Feldspar XX salmon 

Mica XX sil ver Hornblende XX black 

Grain Size: Coarse Medium XX 

Visible Biological Growth No 

Stone Condition: 
Horizontal Areas_ 

Vertical Areas (SWNE) E &. W pol ished__Qn_crQSS , names o n_ 
E arch polished — 

Polished Areas Feld. visable. on W some Feld t urned to 
clay, mica deter, too — — 

Unpolished Areas Feld. not visable 

rnmrnents S vert, only Q g< H VIS, no green biol 



Sample #_ 

Name M^r g.^iret b. Phillips 

Date of Dp^th Sept. 15 1926 
Approx . Years of Exposure 64 

Lot # or Approx. I ncation f-JB^r 84; 

Design of the Mnnnmpnt upright slab w.ith arched top 

Orientation of Upright Stones E _ 

Surface Di5coloration___None 

Minerals (appearance and color): 

Quartz XX Feldspar XX salmon. 

Mica SDjTie Hornblende XX 

Grain Size: Coarse XX Medium. 

Visible Biological Growth Mainly on north side un 

unpolished area oreen aroi>JS mostl y on ho rnblen de, ^-: base 

Stone Condition: 

Horizontal £>-»^<:^ Tnp has pits with y ello w c oLored clay 

Vertical Cr-c^^<:^< '^\^iNF ) W side has pits with yellow or 
light gold colored clay _ 

Polished Q.-^^^ UJ also some areas with re d betw een cracks 
between minerals but not near Feld. _ — _ 

Unpolished Areas^ 




Sample #__3 

Name Noro Phillips Szarlosky 

Date of Death 9 Aug 1885 

Approx . Years of Exposure 105 

Lot # or Appro); . Location NE of church 

Design of the honument horizontal with raised cros; 

Orientation of Upright Stones 

Surface Discoloration Black-does not scrape off 
granular like discoloration 

Minerals (appearance and color): 

Quartz XX Feldspar X X amber 

Mica some Hornblende XX 

Grain Size: Coarse XX Medium_ 

Visible Biological Srowth None 

Stone Condition: 
Horizontal Areas 

Vertical Areas(SWNE) 

Polished Areas flak ing 

Unpol IS he 

pd Area 

s general 



only Fe 

Id . in 





1 Sire 

as near 






a thin 


t exfol 

lating on 

the flat 

diagonal planes f 

acing N 

.?.: S 

also pi 

tting on 





e;;fol . 


remains of ivy 



also do not hav 

e any c 





Sample # 4_ 

Name Chandler Hare. Priest 
Date of Death 1893 

Appro;;. Years of Exposure 9 7 

Lot # or Appro;-!. Location 569 & 570 

Design of the Monument uprig ht cross 
Orientation of Upright Stones E 

Surface tm ^^^,^ nrp,t i nn black or dark green ^reas on 
ho r izontal and onto vert, below 

Minerals (appearance and color): 

Quartz XX Feldspar XX pink 

Mica XX silver Hornblende XX_ 

Grain Size: Coarse Medium XX_ 

Visible Biological Growth spherical an d green 

Stone Condition: 
Horizontal Areas pitting 

Vertical Areas(SWNE) 

Polished Areas none 

Unpolished Areas, 




Sample # 5 

Name Francis Barrinqton 

Date of Death 1S94 

Appro;;. Years of Exposure 96 

Lot # or Appro;;. Location 490 

Design of the Monument greek cross 

Orientation of Upright Stones E_ 

Surface Discoloration black and gr een in pro tected 

areas and on N si de 

Minerals (appearance and color): 

Quartz XX Feldspar XX light amber 

Mica XX silver Hornblende XX 

Grain Size: Coarse Medium XX 

Visible Biological Growth green mostly on black minerals 

Stone Condition: 

Horizontal Areas very rough only guartz and hornblende 


Vertical Areas(SWNE) 

Polished Areas none 

Unpolished Areas_ 




Sample # 6_ 

iM^m>^ Daniel B. McComb/ Catherine B. McComb Hodgson 

Date of Death 1395 — 

Appro;;. Years of Exposure 95 

Lot # or Appro;;. Location 1B3 . 

Design of the Monument cube on base with b rackets. 

Orientation of Upright Stones E_ 

Surface ni ^rol oration black o n unpnl ■ areas protected 

f r om rain — — — — — 

Minerals (appearance and color): 

Quartz XX Feldspar XX yellow/amber 

Mira x7 silver Hornblende — XX 

Grain Size: Hoarse XX Medium 

Visible Biological Rrnwth on N. onl y on b ase on S, W g< E 

Stone Condition: 
Horizontal Areas 

Vertical ak-.^^c= f guNF ^ W side on polished Ar^ A both red & 
green growths under surface sev eral areas with flaking 

Polished Arpas Feld. into clay or open p its, areas o f 

buldges with chipped or fl aked minerals with red .*. green 

Unpolished C^r^!^^'^ l«J side c o oper green discolor, on 

hornblende pokss. biol. growth _ , 

nnmrnents lichen type gro w th on W polished Are^ l"5g both 
crystal flakes around ednes clay particles underneath 



Sample # 1_ 

Name Anna T. Dayton 

Date of Death 1398 

Appro;. Years of Exposure 92 

Lot # or Appro; . Location near 209 

Design of the Monument vertical cross 
Orientation of Upright Stones E 

Surface Discoloration green on N & Ul in streaks 

Mxnerals (appearance and color): 

Quartz XX Feldspar XX faint pink 

Mica some Hornblende XX 

Grain Size: Coarse Medium XX 

Visible Biological Browth green on hornblende horiz g< 
vert E S & l-J sides 

Stone Condition: 

Horizontal Areas 

Vertical Areas(SWNE) 

Polished Areas Feld only vis on pol not on unpol 

Unpolished Areas_ 




Sample # 8_ 

Namg McUJilliam James 
Date of Death 1972 

Appro;;. Years of E;!posure 18_ 

Lot # or Appro;:, location acro ss from 039 

Design of the Monument low vertical slab , dia gonal face 
Orientation of Upright Stones E__ 

Surface Di <^rnT nration some qree 

n & black in small spots 

Minerals (appearance and color): 

Quartz XX ___^__ Feldspar XX salmon 

Mica none Hornblende some 

Grain Size: Hoarse XX Medium. 

Visible Biological Rrnwth on Dol & unpol gr een growths 
on hornb /rough dressed areas spherical green in recessed 

Stone Condition: 

Horizontal Arpas no pitti ng on unpol 

Vertical Areas ( SWNE ) . 

Polished Qrp.^^ mi nerals under biol growths Bre_ 
pitted also red &. green growths btwn cr ystals 

Unpolished Areas 

Commen ts on polished a »-eac; many feldspar had brick 

red stains inside the crystal no biol growth near dift 

from red biol growth between crystal boundaries _ 



Sample # 9 

IsiA^mP W. Elmer Schofield NA/H. Morield Schofield 

Date of Death 1944/1960 

Appro;;. Years of Exposure 46 

Lot # or Appro;;. Location 830 

Design of the Mnniiment Thick Vert R Qug_h_Cut__Sl_ab 

Orientation of Upright Stones E 

Surface deterioration G ree n . 

Minerals (appearance and color): 

Quartz XX Feldspar XX Cloudy white 

Mica XX Silv er Hornblende XX 

Brain Size: Coarse Medium — >i>i 

Visible Biological Growth Green o n H more than Q on 
North Side -l- Protected Areas 

Stone Condition: 

Horizontal Areas 

Vertical Area5(SWNE). 

Polished Areas No ne 

Unpolished Areas 

Commen ts No visible s igns of deterioratio n. 


Sample # 10 

l\l;.mp Albert E. Schof ield/Marger et Mitchell, wife 

Date of np^th 1936/1929 

Appro;:. Years of E>;posLire 54 

Lot # or Appro;:. Location 845 

Design of the Monument Vertical Cro5 S__w/. 
Orientation of Upright Stones — e_ 

carvin gs 

Surface Hi c:;rnl oration Gree n & Black 

Minerals (appearance and color): 

Quartz ;■:>: Feldspar faint amber 

Mica ;■:;■; silver Hornblende x>^ 

Grain Size: Coarse Medium^ 

Visible Biological Rrnwth Spherical green near ground, 
g< on M side — mostly on hornblend e 

Stone Condition: 

Horizontal Areas . — — 

Vertical c^f^^^< ?^UiNF.) Protruding areas of carvi ngs are, 
b 1 ac kened -does not appear to biological . 

Polished Areas None 

Unpolished Areas, 




Sample # 11 

Name Ra Lph M ilton Davis Pries _t_ 
Date of Death 1979 . 

Appro;;. Years of Exposure. 


Lot # or Appro;:. Location Across fro m 774 

Design of the Monument Diagonal face low ve rt. 
Orientation of Upright Stones E___ 

Surface n -i c.r-nl r-,r^ t i nn Green on rough cut a reas. 

Minerals (appearance and color): 

Quartz >:;■; . Fp.1rl<=ipar cloudy white 

Mica ;■;;■; silver Hornblende >i_i< 

Gram Sine: Coarse Medium X_)<_ 

Visible Biological Growth Green on base 

Stone Condition: 
Horizontal Areas_ 

Vertical Area5(SWNE). 

Polished Areas Black/Green Growth on H 

Unpolished Areas 




Sample # JJ 

Name Ada M. lAjalbane 
Date of Death 1979 

Appro;:. Years of E;:po5Lire 11 

Lot # or Appro;; . Location 946 

Design of the Monument Flat rectangular 

Orientation of Upright Stones 

Surface Discoloration none 

Minerals (appearance and color): 

Quartz >;;; Feldspar ;■;;■; F'ink 

Mica Hornblende >;;■; 

Grain Size: Coarse ;■: ; ; Medium 

Visible Biological Growth Green Around Sides 

Stone Condition: 
Horizontal Areas 

Vertical Areas(SWNE) 

Polished Areas Brick Red Spots in F Crystals 

Unpolished Area; 




Sample ti 13 

Name Walbank William Elizabeth J Date of 

Death 1942/1936 

Appro..;. Years of Exposure 54 

Lot # or Approx. Location 933 

Design of the Monument Vertical Gothic Arch S haped_Slab_ 

Orientation of Upright Stones E 

Surface discoloration green near base, bl ack, on t op g<.._..in_ 

protected areas g< in rough dres sed side s 

Minerals (appearance and color): 

Quartz XX Feldspar XX sal mon 

Mica XX black Hornblende XX 

Grain Size: Coarse Medium XX 

Visible Biological Grov^^th black i s biol ■ green gro ws on 

Stone Condition: 

Horizontal areas 

Vertical Areas (SWNE) Some pitting with red stain ing 

Polished Areas N one 

Unpolished Areas 




Sample # 14 

Name Raleigh UJilliam H g< Rose Ella 
Date of Death 1947/1961 

Appro;;. Years of Exposure 43 

Lot # or Appro;;. Location 929 

Design of the Monument Vertical Slab 

Orientation of Upright Stones E 

Surface Discoloration green on base 

Minerals (appearance and color): 

Quar t z XX Fe 1 d spar XX salm o n pink 

Mica XX black Hornblende XX 

Grain Siee: Coarse XX Medium. 
Visible Biological Growth_ 

Stone Condition: 
Horizontal Areas 

Vertical Area5(SWNE). 

Polished Areas Pits with gold clay material 

Unpolished Areas 

Comments Red staining between crystal ed ges, opl 
pol ished 



Sample # 15 

Name Hov^ard J. Yoast 
Date of Death 196 7 

Appro;;. Years of E>;po5ure 23 

Lot # or Appro;;. Location 935 

Design of the Mnnnmpnt Diaa . l-ace low v ertical ajjab. 
Orientation of Upright Stones __E _ 

Surface Hi c^rnloration Only G on bas e 

Minerals (appearance and color): 

Quartz_XX Feldspar XX pink. 

Mica XX black Hornblende — XX 

Grain Si=e: Coarse Medium XX_ 

Visible Biological firowth_ gr een on ba se^ 

Stone Condition: 
Horizontal Areas, 

Vertical Areas(SWNE). 

Polished Areas Areas of dark red staininq-ne ar_ 
pits with gold clay — possib le bu q_5 

Unpolished Areas 




Sample # 16 

Name Knott, Edward, Ruth, 8'. Marsden 

Date of Death 1945/1976/42 

Appro;-!. Years of E;:po5Lire 48 

Lot # or Appro;;. Location 916 

Design of the Monument Vert, tall slab 
Orientation of Upright Stones E 

Surface Discoloration Green &. Black in protected areas 
and on North 

Minerals (appearance and color): 

Quartz XX Feldspar XX amber 

Mica XX silver Hornblende XX 

Grain Size: Coarse Medium ;■;;■; 

Visible Biological Growth Same as surface 

Stone Condition: 

Horizontal Areas Sawn marks partially gone 

Vertical Areas (SWNE) Sawn marks still visible 

Polished Areas none 

Unpolished Areas_ 




Sample # 17 

Name Sarah E. Cole 

Date of Death 1921 

Appro;;. Years of Exposure 69 

Lot # or Appro;;. Location 772 

Design of the Monument Horiz. curved top 
Orientation of Upright Stones 

Surface Discoloration green on unpolished Bre^, black 
around inscription 

Minerals (appearance and color): 

Quartz XX Feldspar XX salmon 

Mica ;•;;•; black Hornblende >::: 

Grain Size: Coarse Medium, 

Visible Biological Growth 

Stone Condition: 

Horizontal Areas no major deter 

Vertical Areas(SWNE) 

Polished Areas 

Unpolished Areas_ 




Sample # 18 

Name Frederic Graff 

Date of Death 1890 

Appro;;. Years of Exposure 100 

Lot # or Appro;;. Location SW of church 

Design of the Monument Horizontal slab 
Orientation of Upright Stones 

Surface Discoloration Black around inscriptions 

Minerals (appearance and color): 
Quartz XX Feldspar XX 

Mica XX Hornblende XX 

Grain Size: Coarse XX Medium 

Visible Biological Growth green growths on hornblende 

Stone Condition: 

Horizontal Areas Many pits some flaking 

Vertical Areas(SWNE) 

Polished Areas Many pits some flaking 

Unpolished Areas, 

Comments Black around letters worse than on 

horizontal than diagonal 



Sample # 19 

Name Fracis Sayre Kent 

Date of Death 1890 

Approx . Years of Exposure 100 

Lot # or Appro;;. Location S of church 
Design of the Monument vertical cross 
Orientation of Upright Stones E 

Surface Discoloration Green &. Black, mostly on 
north &. east 

Minerals (appearance and color): 

Quartz >:>: Feldspar >:>: pink 

Mica ;•;;■; black Hornblende :■;>■! 

Grain Size: Coarse Medium xx 

Visible Biological Growth above 

Stone Condition: 

Horizontal Areas Pitting, sawn marks indistinguishable 

F not visible 

Vertical Areas(SUJNE) F still visible 

Polished Areas None 

Unpolished Areas 




Sample # 20 

Name Robert Fulton Blight 

Date of Death 1898 

Appro;;. Years of Exposure 92 

Lot tt or Appro;;. Location 115 

Design of the Monument Vertical Cross w/ Carvings 
Orientation of Upright Stones E 


Discoloration see below 

Minerals (appearance and color): 

Quartz XX Feldspar XX 

Mica XX 

Hornblende XX 

Grain Size: Coarse 

Medium XX 

Visible Biological Growth Green on North, near base 

^ in protected areas 

Stone Condition: 

Horizontal Areas F g-: M still Visible 

Vertical Areas(SWNE) 

Polished Areas 

Unpolished Areas_ 

Comments__ F' 1 1 1 i n g on d iagonal areas on base, 

Blackenin g a round edges on polish design 



Sample # 21 

Name Albert Casey 

Date of Death 190.: 

Appro)-;. Years of E>;posure 87 

Lot # or Appro;;. Location S of church along wall 
Design of the Monument Vertical thick slab 

Orientation of Upright Stones E 

Surface Discoloration As below 

Minerals (appearance and color): 

Quartz XX Feldspar XX cloudy white 

Mica Hornblende XX 

Grain Size: Coarse Medium XX 

Visible Biological Srowth Some H areas could have 
hemi-lichens by-appearance 

Stone Condition: 

Horizontal Areas Top-unpolished areas almost entirely 

coyered with green & black biol . 

Vertical Areas(SWNE) 

F'ol ished 









Unpol ish€ 

?d Areas 

; Rou 



s^rBEi a 




thick co\ 

of q 









' branc 





Sample # 22 

Name Sidney Hutchinson 

Date of Death 1337 

Appro;-!. Years of Exposure 101 
Lot # or Appro;;. Location Near 124 

Design of the Monument Vertical slab 
Orientation of Upright Stones E 

Surface Discoloration G g< B on base on N side in pro- 
tected areas ____^ 

Minerals (appearance and color): 

Quartz >:;■: Feldspar xx light amber 

Mica ;:;■; ligh t Hornblende ;■;;■; 

Grain Size: Coarse ;■:;■: Medium_ 

Visible Biological Growth 6 on H polished & unpol ished 

Stone Condition: 
Horizontal Areas 

Vertical Area5(SWNE) 

Polished Areas Some pits much red between crystal 

Unpolished Areas F still Visible, no pitting 




Sample # 23 

Name Helen UJilliams, Mary Ulenti^orth Leech 

Date of Death 1945/1965 

Appro;;. Years of Exposure 45 

Lot # or Appro;;. Location South of church door 

Design of the Monument vertical cross 

Orientation of Upright Stones E 

Surface Discoloration G on UJ g/ N, near ground 

Minerals (appearance and color): 

Quartz xx Feldspar >:x light pink 

Mica ;•;>; black Hornblende ;■;>: 

Grain Size: Course Medium ;:;; 

Visible Biological Growth As above 

Stone Condition: 

Horizontal Areas Sawn marks almost all gone mica, some 

F still visible some pitting 

Vertical AreasCSWNE) 

Polished Areas None 

Unpolished Areas 




Sample # 24 

Name Elizabeth Ralston Welsh 
Date of Death 1885 

Appro;;. Years of E>;pQ5ure 105 

Lot # or Appro;;. Location Near to S wall of church 

Design of the Monument 

Orientation of Upright Stones 

Surface Discoloration Much black in unwashed areas, 
G on N and along ba se 

Minerals (appearance and color): 

Quartz ;■;;■; Feldspar >;>; light amber 

Mica Hornblende ;;;■; 

Grain Size: Coarse ;;;■; Medium. 

Visible Edological Growth 

Stone Condition: 

Horizontal Areas Some pitting 

Vertical Areas(SWNE) 

Polished Areas No pitting, very little area is poli shed 

Unpolished Areas 

Commen ts Very good condition 



Sample # 25 

Name Edward Patterson/ Isabel la Liddon Co; 

Date of Death 1910/1907 

Appro;;. Years of Exposure 83 

Lot # or Appro;;. Location NE of church 
Design of the Monument Vertical slab 
Orientation of Upright Stones E 

Surface Discoloration Green on E , N & near base, 
black on protected unwashed areas 

Minerals (appearance and color): 

Quartz ;■;;; Feldspar ;■;:■! salmon 

Mica ;■;;■; black Hornblende >;;■; 

Grain Size: Coarse Medium 

Visible Biological Growth As above, G mostly o n H 

Stone Condition: 

Horizontal Areas much pitting 

Vertical Areas(SUJNE) Unpolished, sawn marks still visible 

Polished Areas Only letters, some pitting wit h clay 

Unpolished Areas 




Sample # 26 

Name Samuel Rodman Morgan 
Date of Death 1891 

Approx . Years of E;;po5ure 99 

Lot # or Appro;;. Location 31 

Design of the Monument Horizontal sl a b w/ raised cross 

Orientation of Upright Stones 

Surface Discoloration Black 

Minerals (appearance and color): 
Quartz :■;;■: Feldspar :■;;; 

Mica >;;■: black Hornblende_ 

Grain Size: Coarse Medium, 

Visible Biological Groi^th G on base 

Stone Condition: 

Horizontal Areas Very p itted 

Vertical Areas(SWNE) 

Po 1 1 shed Areas Edges of letter s ?< raised cross black 

very pitted, vertical less t han ho rizonta l 

Unpolished Areas, 




Sample # 27 

Name Harriet horqan 

Date of Death 1915 

Appro;;. Years of Exposure 75 

Lot # or Appro;;. Location E of church 

Design of the Monument Horizont al w/ c arvings 
Orientation of Upright Stones 

Minerals (appearance and color): 

Quartz ;■;;; Feldspar > 

Mica ;;;•; Hornblende 

Grain Size: Coarse Medium_ 

Visible Biological Growth G on base 

Stone Condition: 

Horizontal Areas Black appears not to be biological , 

ver y pitted, corners of letters broken 

Vertical Areas (SWNE) 

Polished Areas None 

Unpolished Areas 




Sample # 28 

Name James S. Pierie/Georqe I'J . Fierie 

Date of Death 1882/1385 

Appro;;. Years of Exposure 103 

Lot # or Appro;-; . Location E of church 

Design of the Monument Thick vertical slab 
Orientation of Upright Stones _E 

Surface Discoloration Very little, some black oh base 
G on sides near ground 

Minerals (appearance and color): 

Quartz ;■;;■; Feldspar ;■;;; light pinks 

Mica Hornblende :■;;■; 

Grain Size: Coarse ;■;;; Medium 

Visible Biological Growth G o n H 

Stone Condition: 

Horizontal Areas Some pitting 

Vertical Area5(SWNE) 

Polished Areas Some pitting & clay, red between crystals 
some G under surface too 

Unpolished Areas Sawn finishing visible on w side, 

some F into clay 




Sample # 29 

Name John ■?< Barbara J. UJarburton 
Date of Death 1877/1388 

Approx . Years of bi;:pQsure 113 

Lot # or Appro;;. Location N of church 
Design of the Monument 

Orientation of Upright Stones 

Surface Discoloration Much black in unwashed areas, B on 

Minerals (appearance and color): 

Quartz :■;>: Feldspar >:;; Light amber 

Mica Hornblende >;;•; 

Grain Size: Coarse >;;■; Medium 

Visible Biological Growth See a bove 

Stone Condition: 

Horizontal Areas Some pitting 

Vertical Areas(SWNE) 

Polished Areas N o pitt ing , very little area, is polished 

Unpolished Areas 




Sample # 30 

Name llary Ann Wilson 

Date of Death 136." 

Approx . Years of Exposure 127 

Lot tt or Appro;;. Location North of Church 

Design of the Monument Horizontal w/ ca rvi ngs 

Orientation of Upright Stones 

Surface Discoloration Black on raised areas 

Minerals (appearance and color): 

Quartz xx Feldspar xx pink 

Mica XX silver Hornblende 

Grain Size: Coarse Medium XX 

Visible Biological Growth G on bas e 

Stone Condition: 

Horizontal Areas Black appears not to be biological 

very pitted, corners of letters broken 

Vertical Areas (SWNE) Sawn finish visible on sides 

Pol ished 




Unpol IS he 






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Anne & Jerome Fisher 

University of Pennsylvania 

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