Manufacturing china clay opportunities in North Carolina

CI
3:40

North Carolina Sfafe Library
*<•£ Raleigh

North Carolina
Department of Conservation and Development

R. Bruce Etheridge, Director

DIVISION OF MINERAL RESOURCES
Jasper L. Stuckey, State Geologist

bulletin Number 40

manufacturing china clay
opportunities

IN

NORTH CAROLINA

RALEIGH
1941

NX

D°c North Carolina

Department of Conservation and Development

R. Bruce Etheridge, Director

DIVISION OF MINERAL RESOURCES
Jasper L. Stuckey, State Geologist

bulletin Number 40

manufacturing china clay
opportunities

IN

NORTH CAROLINA

RALEIGH
1941

Otorth

<***, *«* library

MEMBERS OF THE BOARD OF CONSERVATION AND

DEVELOPMENT

Governor J. Melville Broughton, Chairman Raleigh

Santford Martin, V ice-Chairman Winston-Salem

Harry Bailey Spruce Pine

Oscar Breece Fayetteville

Bruce Cameron Wilmington

K. Clyde Council Wananish

W. J. Damtoft Asheville

J. Horton Doughton Statesville

Irving F. Hall ■_ Raleigh

Roy Hampton Plymouth

J. L. Horne, Jr j Rocky Mount

William Carl Hudson Morganton

Charles H. Jenkins P Aulander

Paul E. Jones Farmville

Carroll P. Rogers Tryon

Richard Tufts Pinehurst

R. Bruce Etheridge, Director

TABLE OF CONTENTS

Page

Letter of Transmittal 5

Foreword :::_:;: 6

Introduction l 7

Description and Location of Mineral Deposits 7

Typical Analyses of Spruce Pine Alaskite 10

Present Kaolin Deposits 10

Analyses of Refined Kaolin Samples 11

Available Supply of Kaolin 11

Refining Kaolin 13

Electric Firing 15

Bureau of Mines 17

Resistor : 17

Results of Electric Firing Tests 19

Rate of Firing 19

Economics of Electric Firing 21

Comparative Energy Costs 21

Availability of Furnace 24

Present Southeastern Market 24

LIST OF ILLUSTRATIONS

Figure Page

1. Index Map Showing Location of North Carolina

Kaolin Deposits 8

2. North Carolina Residual Alaskite Kaolin Deposits 9

3. Mine of Kaolin, Inc., Spruce Pine, N. C 12

4. Plant of Kaolin, Inc., Spruce Pine, N. C 12

5. A Mine of Harris Clay Company, near Spruce Pine,

N. C 14

6. Clay Preparation Machinery, Harris Clay Com-

pany Plant near Spruce Pine, N. C 14

7. A Feldspar Plant in North Carolina . 16

8. Electric Periodic Kiln at Electrotechnical Labora-

tory of U. S. Bureau of Mines, Norris, Tennessee- 18

9. Casting Room at Electrotechnical Laboratory of

U. S. Bureau of Mines, Norris, Tennessee 20

10. Electric Tunnel Kiln at Electrotechnical Labora-

tory of U. S. Bureau of Mines, Norris, Tennessee— 20

11. Test Ware Produced Experimentally at TVA

Ceramic Laboratory. Made Exclusively of
North Carolina Kaolins and Other Domestic
Materials 22

12. Test Ware Produced Experimentally at TVA

Ceramic Laboratory. Made Exclusively of
North Carolina Kaolins and Other Domestic
Materials 23

LETTER OF TRANSMITTAL

Raleigh, North Carolina
May 1, 1941

To his Excellency, Hon. J. Melville Broughton,
Governor of North Carolina.

Sir : I have the honor to submit herewith, as Bulletin
No. 40, a report on china clay manufacturing opportuni-
ties in North Carolina. For many years, many have held
the opinion that the manufacture of china clay offers
advantages in our State.

This report summarizes investigations and research
directed toward leading the way to the exploitation of
the mineral resources of the State which are the raw
materials of the industry. It is hoped that this
publication will give information which will be helpful
in bringing new manufacturing enterprises to North
Carolina.

Yours respectfully,

R. Bruce Etheridge,
Director.

FOREWORD

The present report entitled "Manufacturing China
Clay Opportunities in North Carolina" has been pre-
pared to set forth in brief, the possibilities of producing
high-grade ceramic products from local materials in
Western North Carolina. The report is not the work of
any one person but rather represents a summary of the
field investigations and laboratory research carried on
by the Tennessee Valley Authority and the United States
Bureau of Mines over a period of several years. These
investigations were greatly facilitated by the friendly
cooperation of the various operators of the Spruce Pine
District and adjoining areas.

The investigations summarized in this report indi-
cate that North Carolina contains large reserves of
minerals and materials, to which only a minimum
amount of accessory clays need be added in order to pro-
duce high-grade ceramic wares by modern methods. The
close proximinity of these accessory clays to the large
reserves of North Carolina raw materials and the ex-
istence of a ready market in the Southeast suggest
splendid opportunities for the establishment of an in-
dustry in Western North Carolina based on the utiliza-
tion of these resources.

Jasper L. Stuckey,
State Geologist.

MANUFACTURING

CHINA CLAY OPPORTUNITIES IN

NORTH CAROLINA

INTRODUCTION

An ample supply of fine china clay is found in the
Spruce Pine District of North Carolina. Of special
interest to the ceramic industry is the extremely low iron
content and the occurrence of only a trace of titanium
in the kaolin. An exceptionally fine grade of kaolin is
now being produced for the china clay trade by two
modern refining plants and several older plants located
near Spruce Pine, North Carolina. This kaolin is also
being used for various fillers and special products.

Although kaolin has been produced from the Spruce
Pine Area for more than a half century, its potentialities
are not yet generally recognized, and the purpose of this
booklet is to acquaint ceramic manufacturers with the
possibilities of manufacturing chinaware in the south-
east close to supplies of raw material and tapping an
under-developed but growing retail market.

Description and location of Mineral deposits

These kaolin deposits have been formed from huge
bodies of coarsely crystalline, white granite, ALASKITE,
containing practically no iron-bearing minerals. The
Spruce Pine alaskite has its greatest development in the
vicinity of Spruce Pine, Mitchell County, North Caro-
lina, and outcrops at irregular intervals over an area
of about 225 square miles. The largest unbroken body
occurs two miles northwest of Micaville, Yancey County,
North Carolina, and has an outcrop width of about one
mile and a length of about two and one-half miles.
Occasional small Spessartite-like (manganese-iron) gar-
nets are found in the alaskite, but hornblende is entirely

8

Manufacturing China Clay Opportunities

ill yy f<

\ Jt>A

Irs Ms

so

©

O
Q

e

si

•^*
^^

o

j-

<s

■i«J.
*n

O

O

Si

©

e

o

o

©>

o

2Q

©>

5

In North Carolina

9

e

e

c

fc

QQ
W

9

10 Manufacturing China Clay Opportunities

absent. Biotite, the high iron mica, is rarely found in
the alaskite, although frequently associated with the
pegmatite cutting the alaskite. Most granites and
pegmatites contain various titanium minerals, but the
Spruce Pine alaskite is an exception in that it contains
no noticeable titanium minerals.

TABLE I

TYPICAL ANALYSES OF SPRUCE PINE ALASKITE

No. 1 No. 2
Percent Percent

Si02 73.96 74.30

A1203 15.77 15.50

Fe203 0.33 0.30

CaO 1.30 0.90

K20 3.74 4.56

Na20 4.57 4.15

Ignition Loss 0.31 0.26

Total ."_ 99.98 99.97

The analyses of Table I are from the Minpro Labora-
tory, United Feldspar and Minerals Corporation, Spruce
Pine, North Carolina.

The deposits are outstanding in the uniformity of
the mineral content. All the alaskite bodies are essen-
tially of the same composition and texture and are
remarkably uniform throughout their extent. The pro-
portions of feldspar, quartz, and mica vary only slightly
within the bodies. The alaskite referred to in Table I
contains 45.3 percent plagioclase feldspar, 2.12 percent
microcline feldspar, 28.6 percent quartz, 2.2 percent
muscovite mica, 0.5 percent garnet, 1.2 percent clays,
and 1.0 percent other minerals.

PRESENT KAOLIN DEPOSITS

More than 50 geographically separate kaolin deposits
associated with the Spruce Pine alaskite, have been found
in Avery, Mitchell, and Yancey Counties, North Carolina.

In North Carolina 11

The largest and best of these residual deposits occur
under terrace levels produced by the North and South
Toe Rivers and Crabtree Creek. Practically all of the
deposits contain recoverable kaolin and rarely occur with
objectionable mining features, such as excessive over-
burden and inaccessible locations. The beds are easily
mined either by mechanical means or by water jets under
moderate pressure. One deposit near the town of Spruce
Pine is reported to have been mined to a depth of slightly
more than 100 feet.

s

TABLE II

ANALYSES OF REFINED KAOLIN SAMPLES

No. 1 No. 2

Percent Percent

Si02 47.94 46.18

A1203 37.02 38.38

Fe203 -, - 0.60 0.57

Ti02 0.02 0.04

CaO 0.30 0.37

MgO 0.07 0.42

K20 1.25 0.58

Na20 0.06 0.10

Zr02 0.08

Ignition Loss 13.03 13.28

Total 100.29 100.00

The analyses of Table II were furnished by Kaolin,
Incorporated, and Harris Clay Company, Spruce Pine,
North Carolina.

Available Supply of kaolin

It has been reliably estimated(1) that 51,000,000 tons
of crude kaolin exist in Avery, Mitchell, and Yancey
Counties, North Carolina. By crude kaolin is meant the
kaolin and its accompanying matrix minerals less the

(i) Paul M. Tyler and A. Linn: "Minerals Yearbook — United States Bureau
of Mines. 1940." Page 1255.

12

Manufacturing China Clay Opportunities

Figure 3. Mine of Kaolin, Inc., Spruce Pine, N. C.

Figure 4- Plant of Kaolin, Inc., Spruce Pine, N. G.

In North Carolina 13

schist and gneiss inclusions. The percentage of recover-
able kaolin varies with the various deposits. Many de-
posits have been worked on a 10 percent or greater
recovery basis. A higher percentage than 10 percent of
recoverable kaolin, however, occurs in many deposits.

In addition to kaolin, these deposits yield valuable
by-products from the kaolin refining process, such as
high-grade muscovite mica used in the manufacture of
roofing and as fillers, and semirkaolinized feldspar and
quartz. The quartz is milky white, free from iron stains,
and near the specifications for high-grade glass sand,
although little use has so far been made of it for this
purpose.

REFINING KAOLIN

In 1936, the Tennessee Valley Authority established
a ceramics laboratory at Norris, Tennessee, to work out
methods of refining North Carolina kaolin in order to
produce all-American clay bodies suitable for the manu-
facture of high-grade and medium-grade chinaware, and
to replace imported kaolin. These experiments were car-
ried out jointly with the U. S. Bureau of Mines and the
Harris Clay Company of Spruce Pine, North Carolina,
and in 1938 a new modern kaolin refinery was built in
the Spruce Pine District. About the same time Kaolin,
Incorporated, also of Spruce Pine, North Carolina, set
up a large plant to refine kaolin by a process developed
in Czecho-Slovakia. Both companies are now supplying
a blended kaolin of uniform quality to the trade which
is equal to the best imported kaolin.

The TVA process is available to other prospective
producers or manufacturers. Shipments of over 12,000
tons of refined kaolin per year are now being made to
northern potteries.

In addition to the kaolin, there are potash, soda, and
blended feldspars produced in the area which are used

14

Manufacturing China Clay Opportunities

Figure 5. A Mine of Harris Clay Co., near Spruce Pine, N. C.

Figure 6. Clay Preparation Machinery, Harris Clay Company Plant near

Spruce Pine, N. C.

In North Carolina 15

in the ceramic industry. This area contains the largest
reserves of high-grade feldspar known in the United
States, and has produced an average of 82,700 tons an-
nually for the past decade. This material is produced
by three large, modern grinding plants in the Spruce
Pine area. One of these plants produces ground quartz
in addition to the feldspar. It might also be of interest
to the ceramist to know that the only pyrophyllite
(H2AI2 (SiOs)4) mines and grinding plants in the United
States are located in North Carolina. This industry is
located in Moore and Randolph Counties, about 200 miles
east of the Spruce Pine District, where three modern
grinding plants are in operation. In these counties there
are large reserves of high-grade crystalline pyrophyllite.
Both foliated and fibrous or radiating varieties are
abundant. Another important ceramic mineral in the
Spruce Pine District is kyanite (ALSiOr.), which occurs
commonly throughout most of the Mountain and much of
the Piedmont sections of the State. The most important
deposits are found on the western edge of the Spruce
Pine District, in a belt 6 to 8 miles wide, extending from
near Burnsville, Yancey County to Swannanoa, Bun-
combe County. The mineral occurs in metamorphosed
acid rocks and in pegmatite dikes and quartz veins, in-
closed in these rocks. There are ample reserves of
kyanite-bearing gneisses and schists which contain from
5 to 40 percent of kyanite. A modern beneficiation plant,
capable of producing a 98 percent kyanite concentrate is
in operation near Burnsville.

ELECTRIC FIRING

In order to test fully the use of North Carolina
kaolins for high-grade dinnerware, the TVA built and
operated at Norris, Tennessee, a small experimental or
pilot plant in which was installed a continuous electric
kiln. Different types of ware of good commercial quality

16

Manufacturing China Clay Opportunities

C5
5=

Si

In North Carolina 17

were made using domestic materials only and fired elec-
trically. Kaolin from North Carolina was blended with
that from Florida to give an ail-American all-kaolin
mixture. A high-grade, vitreous, translucent dinner-
ware was made in order to test thoroughly the best
methods of blending the clay bodies and of molding and
firing the ware. Best results seem to be obtained when
approximately 12 percent of Florida kaolin or ball clay
from Tennessee or Kentucky are added. The proximity
of the Florida kaolins and the Tennessee and Kentucky
ball clays to the Spruce Pine District make possible in
this area the manufacture of an all-Southern body with-
out the necessity of transporting these accessory clays
great distances.

bureau of Mines

The Norris Ceramic Laboratory was recently turned
over to the U. S. Bureau of Mines, who are continuing
the experiments on electric firing and the development
of southern raw materials for ceramic and other uses.
The Bureau of Mines is also testing the production of
large sanitary ware on a small commercial scale using all
American materials under methods of electric firing.

The Bureau of Mines reports that "The North Caro-
lina kaolins correspond most closely of those tested to the
English kaolins in physical and chemical properties, but
as now prepared by improved methods, are finer grained,
more plastic and stronger than English clays."

The Bureau also reports that "North Carolina Alas-
kite was found to represent a satisfactory and enormous
potential source of white-firing, mixed potash and soda
feldspar (plus flint) for many future generations."

RESISTOR

In order to retard oxidation and prolong the life of
the heating element, the ceramic laboratory developed a

18

Manufacturing China Clay Opportunities

itlllf
ililliliipli

Figure 8. Electric Periodic Kiln at Electroteclmical Laboratory of U. 8.

Bureau of Mines, Norris, Tennessee.

In North Carolina 19

graphite core resistor enclosed in a refractory tube of
silicon carbide, in which hydrocarbon gas (propane) was
held under a slight pressure.

The latest tests on graphite resistors protected by a
bonded silicon carbide tube, show a life of from 3,120 to
4,872 hours of continuous firing and an average life of
about 3,800 hours or about 6 months' operations. The
use of these resistors is available under license for other
purposes in the fields of heat treatment, metallurgy,
electro-chemistry, etc.

Results of electric firing tests

The results obtained by firing large sanitary wares
and masses of full size brick, substantiated by theoretical
calculations, have shown that

1. Radiated heat is the major method of transmis-
sion at incandescent temperatures.

2. Firing schedules similar to those in combustion
fired kilns can be maintained by electric firing.

3. Commercial requirements for quality and uni-
formity of vitrification can easily be met if time
is given for "soaking" or completing the reac-
tions at the maximum temperatures.

These results also substantially confirm the experi-
ence in firing thin translucent dinnerware.

RATE of firing

High grade dinnerware has been bisque-fired satis-
factorily in 18-hour cycles for the open setting to 36-hour
cycles for plate bungs and heavy ware. The experimental
kiln at the Norris Laboratory measures 55 feet long, 2
feet and 11 inches wide, and 1 foot high to the spring of
the arch (the kiln has two tunnels each with 1 foot by 1
foot loading cross section), with a total of 14 heating
elements, requires 85 to 110 kw. input, depending upon
operating temperature, and has operated for over 8,500

20

Manufacturing China Clay Opportunities

Figure 9. Casting Room at Electroteclinical Laboratory of U. 8. Bureau of

Mines, Norris, Tennessee.

* c — -■"■

giiiii

Figure 10. Electric Tunnel Kiln at Electroteclinical Laboratory of U. 8.

Bureau of Mines, Norris, Tennessee.

In North Carolina 21

hours on all types of ware from fine china to face brick
with ranges of temperature up to cone 14, 2550° F. The
rates of firing used were faster than those now employed
in the larger commercial, combustion-fired kilns, but
these undoubtedly can be met in other small kilns.

ECONOMICS OF ELECTRIC FIRING

At present with electric energy at 2 mills per KWH
the equivalent electrical energy consumed is comparable
in fuel cost of natural gas at $0.58 per M feet, fuel oil
at 8.4 cents per gallon, and coal at $16.25 per ton.

COMPARATIVE ENERGY COSTS

100% 100% ratio to electricity1

Electricity Oil Gas Coal

2 mill 8.40 580 $16.25

100% 80% ratio to electricity

2 mill - 6.70 46.50 $13.00

3 mill 100 700 19.50

100% 60% ratio to electricity

2 mill 50 350 $ 9.75

3 mill 7.50 52.50 14.60

4 mill 100 70^ 19.50

100% 40% ratio to electricity

2 mill 3.40 230 $ 6.50

3 mill 5.10 350 9.75

5 mill 8.40 580 16.25

Electricity : cost in mill per kwh = 3412 B.t.u.
Oil : cost per gallon, 142,000 B.t.u. per gallon.
Gas: cost per thousand cubic feet, 1000 B.t.u. /cu. ft.
Coal: cost per ton, 14,000 B.t.u. /lb.

i Different types of kilns operate at different degrees of efficiency. The
above table gives cost comparisons for different efficiency ratios as com-
pared to electricity. For example, in a kiln with an SO percent ratio of
efficiency as compared to electricity, electricity at 3 mills per KWH would
represent the same energy cost as fuel oil at 10 cents a gallon, natural
gas at 70 cents per M feet, or coal at $19.50 a ton.

22

Manufacturing China Clay Opportunities

Figure 11. Test Ware Produced Experimentally at TV A Ceramic Laboratory .
Made Exclusively of North Carolina Kaolins and Other Domestic Materials.

Figure 12. Test
Ware Produced
Experimentally at
T V A Ceramic
Laboratory. Made
Exclusively of
North Carolina
Kaolins an$ Other
Domestic Mate-
rials.

lar8'62SL

24 Manufacturing China Clay Opportunities

Electric firing offers :

1. The clean oxidizing atmosphere of the best muffle
kiln designs.

2. The most efficient methods of temperature con-
trol.

3. The most efficient use of energy since there are
no losses of heat from stacks nor radiation from
open, exposed fire boxes.

4. Possible savings in fuel costs in those districts
having high oil or gas prices and low electricity
rates.

5. The opportunity of using multiple tunnel kilns
with more uniform distribution of heat units
and greater savings.

Availability of furnace

The use of the electric tunnel kiln at Norris, Ten-
nessee, is available to ceramic manufacturers desiring
to conduct their own tests of electric firing. Electricity
will be supplied by the TVA at standard commercial
rates. Extra labor, supplies, repairs, and miscellaneous
expenses of operation can be supplied at actual cost plus
a small percentage for overhead and handling.

PRESENT SOUTHEASTERN MARKET

Based on 1935 Census of Manufactures, the estimated
annual market for whiteware in the nine southeastern
states is $10,361,000, of which $9,770,000 worth is pro-
duced outside the area. This includes not only china-
ware, but sanitary and plumbing ware.

The market for chinaware in the Southeast not cov-
ered by production in the area and sold through depart-
ment stores and five and ten stores is conservatively
estimated to be about $3,325,000 annually.