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THE UNIVERSITY
OF ILLINOIS

LIBRARY

AMBER

ITS PHYSICAL PROPERTIES AND
GEOLOGICAL OCCURRENCE

BY
OLIVER C. FARRINGTON
Curator of Geology

FIELD MUSEUM OF NATURAL HISTORY

CHICAGO
1923

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FIELD MUSEUM OF NATURAL HISTORY
DEPARTMENT OF GEOLOGY
CHICAGO, 1923

LEAFLET NUMBER 3

Amber
Its Physical Properties and Geological Occurrence

Amber is a fossil gum of trees of the genus Pinus.
Normally it is yellow in color, varying in shade, how-
ever, from pale yellow to dark brown, and occasionally
being whitish, greenish, or bluish. Very rarely,
amber of a deeper green or blue color occurs. Such
amber is always turbid or cloudy, the turbidity being
due to the presence of numerous air-bubbles. The
modification produced in rays of light by passing
through the bubbles creates these colors.

In transparency all graduations may occur in
amber, between that which is perfectly clear and that
which is wholly opaque. Of the cloudy forms, several
varieties are distinguished in trade, the most im-
portant being “bastard,” “bony,” or “osseous,” and
“frothy” amber. Bastard amber is a somewhat turbid
form of amber, but takes a good polish; bony amber
is opaque, relatively soft, and does not polish well.

The hardness of amber is 2 to 2.5. It therefore
cannot be scratched by the finger nail, but easily
and deeply with a knife. It is also brittle. Its specific
gravity is scarcely greater than that of water, the
exact specific weight being 1.05-1.096. It thus almost
floats in water, especially sea-water. On being heated
amber becomes soft at 150° C., and at 250° to 300°
melts. It also burns readily and at a low temperature,
a fact which has given rise to the name of Bernstein,
by which the Germans know it, and to one of the
Latin names for it, lapis ardens. Rubbed with a cloth

[25]

2 . FIELD MUSEUM OF NATURAL HISTORY

oe EES o
COOKS
sees XXX YA

FISHERMEN FISHING FOR AMBER
FROM AN OLD DRAWING PUBLISHED IN 1677

[ 26]

—— = 1

. ee

AMBER 3

it becomes strongly electric, attracting bits of paper,
etc. Our word “electricity” comes from the Greek
word elektron, which was their name for amber.
Amber was one of the first minerals in which electrical
properties were noted. Being a poor conductor
of heat, amber feels warm rather than cold in the
hand. In this respect it differs from most minerals.
It is attacked but slowly by alcohol, ether, and similar
solvents, a property by which it may be distinguished
from most modern gums and some other fossil ones.
In composition it is an oxygenated hydrocarbon, the
percentage of these elements being in an average
sample: Carbon: 78.94, Hydrogen: 10.53, and Oxy-
gen: 10.53. The mineralogical name of amber is
succinite, a word delivered from the Latin sucinum
(“amber’’). One of its constituents is the organic
acid called succinic acid.

The present source of most of the amber of
commerce is the Prussian coast of the Baltic Sea,
between Memel and Dantzig, although it is found as
far west as Schleswig-Holstein and the Frisian Is-
lands, and even occasionally on the shores of Denmark,
Norway, and Sweden. From time immemorial pieces
of amber have been cast upon the shore in these lo-
calities, and their collection and sale have afforded a
livelihcod to coast-dwellers. Such amber is called “sea
stone,” or “sea amber,” and is superior to that ob-
tained by mining, since it is usually of uniform quality,
and not discolored and altered on the surface. Owing
to its lightness, this amber is often found entangled in
seaweed, and the collectors are accustomed to draw
in masses of seaweed and search them for amber.
Amber so obtained is called “scoopstone,” because nets
are sometimes used to gather in the seaweed. In

marshy regions men on horseback, called amber riders,

follow the outgoing tide and seek the yellow gum.
It is also searched for by divers to some extent.

[27]

4 FIELD MUSEUM OF NATURAL HISTORY

_ From the earliest times the title to this amber
has vested in the State, and either its collecting has
been done under State control, or, a tax is levied
upon it. This tax is levied both on the amber that is
mined, and that obtained from the sea, and brings a
considerable revenue.

Up to 1860 the methods of procuring amber were
largely confined to obtaining it in the manner above
noted. As it was evident, however, that the sea amber
came from strata underneath, and that if, either by
dredging or mining, these strata could be reached, a
much larger supply could be obtained, exploration was
carried on by mining methods with successful results,
and the principal amount of the amber of commerce is
now so obtained. The strata, as shown in the mines
of Sammland, the rectangular peninsula of East
Prussia, where most of the mining is carried on, are:
First, a bed of sand; below this a layer of lignite with
sand and clay; and following this a stratum of green
sand, fifty or sixty feet in thickness. While all these
strata contain scattered pieces of amber, it is at the
bottom of the green sand layer that the amber chiefly
occurs, in a stratum four or five feet thick, and of
very dark color. It is called the “blue earth.” This
stratum is of Tertiary age, and there can be no doubt
that its amber represents gum fallen from pines which
grew at this period, and whose woody remains are
represented to some extent in the layer of lignite. It
is probably true, also, that amber has been collected
here from older deposits.

One of the most interesting proofs of the vegetable
origin of amber is the occurrence in it of insects,
sometimes with a leg or wing separated from the body,
showing a struggle to escape. It is obvious that the in-
sect must have alighted upon the gum when that was
in a viscid state and was held until covered by later
exudations. These insects include spiders, flies, ants,

[28]

INSECTS IN AMBER.

AMBER 5

-and beetles, and even feathers of birds have been found

thus preserved. Remains of plants, such as needles
of conifers, oak leaves and other leaves, buds and
blossoms, are also found preserved in amber. Indeed
the variety of forms preserved in this way is so large
as to indicate that the forests which produced the
amber had a rich flora and fauna. As compared with
modern forms, these plants and animals are found to
belong to existing genera, but the species, with few
exceptions, are peculiar to the region and period.
Through the remains thus preserved, the amber de-
posits have furnished important contributions to our
knowledge of Tertiary life.

Inasmuch as pieces of amber bearing such re-
mains are valued more highly than ordinary amber,
unscrupulous persons have at times found profitable
employment in boring cavities into pieces of amber,
introducing insects or other small animals into them,
and having then filled up the hole with some modern
gum of the same color, or fused the opening over, have
placed them upon the market. It is probable that
all amphibious or marine animals seen in amber have
been introduced this way.

Amber, often of greater beauty than that from
’ Prussia, comes from Sicily. The beauty of the Sicilian
amber consists in the variety of colors it displays,
blood-red and chrysolite-green being not uncommon;
and in the fact that these often exhibit a fluorescence,
glowing within with a light of different color from the
exterior. Chemically the Sicilian amber is not the
same as the Prussian, as it contains less succinic acid,
and it is somewhat more soluble. In other respects
it is not essentially different. It occurs chiefly on the
eastern and southeastern coasts of the Sicilian islands,
being washed up in a manner very similar to the
Prussian amber.

[29]

6 FIELD MUSEUM OF NATURAL HISTORY

Amber has been found in several places in the
United States, but little has proved of commercial
value. It is mostly connected with the Cretaceous
glauconitic, or green sand deposits of New Jersey,
fragments being frequently found there. This amber
is of yellow color, but not so compact or lustrous as

foreign amber. Amber has also been reported from -

the marls of North Carolina, some of the coal-beds
of Wyoming, and in connection with lignite in Alaska.
In the latter region the natives are said to carve it
into rude beads.

Besides Prussia and Sicily, amber occurs in small
quantities in several other countries of Europe, such
as near Basle, in Switzerland; near Paris, in France;
and near London, in England. It is also found in
many parts of Asia, these localities being a source of
supply to the Asiatic countries, such as China and
India. Occasionally amber is obtained from Mexico
which has the beautiful fluorescence of the Sicilian
article, but the exact locality whence it comes is in
doubt.

Besides the counterfeiting of inclusions of amber
there are several substitutes for the gum itself. These
are chiefly celluloid and glass, the former being danger-
ous if used in the manufacture of smoker’s articles,
on account of its inflammatory character. Celluloid
can be distinguished from amber by the fact that
when rubbed it does not become as electric, and gives
off an odor of camphor instead of the somewhat aro-
matic one of amber. Celluloid when dipped in hot
water also gives an odor of camphor. It is also
quickly attacked by alcohol, or ether, and when
scraped with a knife, gives a shaving rather than a
powder, as amber does. Amber, as already noted, is
but slowly attacked by alcohol. Glass can be distin-
guished from amber by its cold feel and greater hard-
ness and specific gravity.

[30]

—— Save

AMBER 7

Besides these substitutes, it has been found pos-
sible by heating and pressing scraps of amber not
large enough for carving, to make them into a homo-
geneous mass, which is sometimes sold as amber and
sometimes as amberoid.

Amber is worked to desired shapes by turning it
on lathes, or by cutting by hand. By heating it in -
linseed oil it becomes soft, so that it can be bent, and
often all opaque spots can be made to disappear. It
can also be colored during this treatment.

Nearly one-half of the total production of amber
is devoted to the manufacture of articles for the use
of smokers, such as cigar and cigarette-holders, mouth-
pieces for pipes, etc. Ornamental objects in great
variety are also manufactured from it, the commonest
of such articles being beads, rounded or faceted and
perforated so that they can be strung together for
necklaces, bracelets, rosaries, etc. These find sale in
all parts of the world, the tastes of people of different
countries being said to vary as to the kind of amber
desired. Thus in Russia and France, for example, the
fine bastard amber is preferred, in Holland and China
the clear variety is wanted, while in West Africa the
demand is for the semi-osseous kind with a brownish
tinge. Pressed amber is suitable for cheap, relatively
bulky articles, but is not adapted for fine manufac-
tures, since after a time it has a tendency to turn white.
The use of amber for varnish is another important
utility, impure or small pieces being chiefly employed
for this purpose.

Specimens illustrating many of the features of
amber enumerated in the preceding pages may be seen
in Hall 34 of the Department of Geology of the Museum
in a case located at about the center of the hall.

OLIVER C. FARRINGTON.

[31]

CONGLOMERATE OF AMBER DROPS.

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