Mineral Facts and Problems: 1960 Edition Page: 205
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muds. In others, clay may be only one of
several satisfactory raw materials available.
The available supply of kaolin and ball clay
for use in the production of whiteware also
affects the demand for feldspar, ground silica
(potter's flint) and various other mineral com-
ponents. There is also an interdependence of
the fire-clay refractories industry and the
metallurgical industries.
High-alumina clays (fire clay and kaolin)
are a potential source of alumina for aluminum
production, but costs are currently too high
for clay to compete with bauxite for this pur-
pose in the United States. In 1958, however,
The Anaconda Co. began operating a 50-ton-
per-day pilot plant in Anaconda, Mont., to
produce aluminum-grade alumina from the
clay of Latah County, Idaho.
Clay or shale is utilized to balance the alu-
mina and silica content of the raw-material
mix at many cement plants.
Fire clay and kaolin have a complex rela-
tionship with a wide variety of other refrac-
tory materials, including silica, dolomite, mul-
lite, magnesite, chromite, graphite, pyrophyllite,
bauxite, olivine, silicides, carbides, nitrides,
borides, and rare-earth oxides. Considerations
governing the selection of a specific refractory,
in addition to P.C.E., are bonding qualities,
load-bearing strength under operating tem-
peratures, and resistance to spalling and
slagging. The relationship of refractory clays
to bauxite is close, as many refractory products
are mixtures of clay and bauxite.
SUBSTITUTES
For ceramic purposes there are no direct
substitutes for clays, although there are alter-
nate materials for almost all clay products.
Wood, glass, concrete, plastics, various metals,
and other materials may be used in place of
ceramic clay products.
For most nonceramic uses there are substi-
tutes for clays. For example, carbon black has
replaced clay to a degree as a filler in rubber
for tires and certain other rubber products.
Several materials, such as talc, gypsum, and
chalk, may be used partially to replace clay as
paper fillers. Several substitutes have been
found to replace fuller's earth and bentonite
as oil clarifiers. In many nonceramic uses,
clays are used because they are less expensive
than other materials having equal or better
qualifications.
Bauxite is a substitute for fire clay in re-
fractory uses and activated bauxite competes
with activated bentonite and fuller's earth in
mineral oil bleaching and filtration. Cinders,
blast-furnace slag, pumice, and perlite aresubstitutes for expanded clay and shale light-
weight aggregate in some uses. Argillaceous
limestone (cement rock), where available, re-
duces or eliminates the need for clay in manu-
facturing cement.
SYNTHETICS
Several clay minerals have been synthesized.
The work was begun by German chemists, and
some was done by the National Bureau of
Standards (10). All work was conducted on
a laboratory scale and was done largely to
establish the correct chemical compounding
and obtain the probable geological conditions
under which the .mineralization may have oc-
curred. The bulk of the work was conducted
on kaolinite, but dickite, beidellite, and non-
tronite were also synthesized. The synthesis
of clay minerals is not difficult, because the
pressures and temperatures required are rela-
tively low (about 2,000 atmospheres and 300
to 400 C.). Synthesis is done in hydrothermal
bombs.
RESERVES
The principal kaolin reserves in the United
States are in large deposits in Florida,
Georgia, South Carolina, and North Carolina.
There are many scattered small deposits usu-
ally of poorer grade material, along the Ap-
palachians, and in a few of the Western
States. According to available estimates, the
measured kaolin reserve is adequate for 35 to
50 years, based on the 1958 rate of consump-
tion.
The measured reserve of ball clay of white-
ware grade in western Kentucky and Tennes-
see is enough for perhaps 50 years, based on
the 1958 rate of consumption. Data are not
available on the extent of reserves in other
States.
The resources of fire clay and miscellaneous
clay supplying the structural trades are vir-
tually unlimited, and reserves are well dis-
tributed throughout the United States. How-
ever, resources of high-grade fire clay used for
refractory purposes occur in only about one-
third of the States; the bulk of these is largely
in only three or four States. The very top
grades, such as the flint and diaspore clays,
show definite signs of depletion. Although
Ohio is one of the largest producers of fire clay
for refractories, the flint variety virtually dis-
appeared some years ago. Pennsylvania and
Missouri, the next largest producers, still have
such clays, but the deposits are approaching
depletion. There are some unexplored sec-
tions, such as eastern Kentucky and Tennessee,
where there are good possibilities of finding
high-grade fire clays. Resources of high-grade205
CLAYS
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United States. Bureau of Mines. Mineral Facts and Problems: 1960 Edition, report, 1960; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc38790/m1/213/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.