GRAPHITE
By Harold A. Taylor, Jr.
Mr. Taylor, a physical scientist with 27 years of industry, Federal Government,
and U.S. Bureau of Mines experience, has
been the commodity specialist for graphite since 1980. Domestic survey data
were prepared by William Field, statistical
assistant; and international data tables were prepared by Amy Durham, international
data coordinator.


Amorphous graphite was not mined
domestically in 1993. Graphite supplies
again exceeded industrial demand. Most
prices of the major kinds of graphite
dropped somewhat or remained
unchanged from those of 1992. Quoted
prices mostly reflected the existing
oversupply. Production of manufactured
graphite and graphite fibers decreased
slightly and increased 21%, respectively.
DOMESTIC DATA COVERAGE


Domestic production data for synthetic
graphite are developed by the U.S.
Bureau of Mines from a voluntary survey
of domestic producers.   Of the 29
operations polled, 100% responded. This
represented 100 % of the total production
data shown in table 4. (See table 1.)
BACKGROUND


Definitions, Grades, and Specifications
Graphite, a soft crystalline form of
carbon, has been called plumbago and
black lead. It crystallizes in a lamellar
hexagonal system, has a gray to black
metallic luster, and is greasy to the feel.
It is anisotropic in its physical properties
and has a weak plane of cleavage parallel
to the lamellae.
The term "amorphous" when applied
to graphite is a misnomer. The term
"microcrystalline" is more descriptive.
The definition of amorphous, as applied
to graphite, has been complicated firther
by longstanding industrial application of
the term to very fine particles of
crystalline flake graphite that can be sold
only for low-value use such as foundry


facings. Fine-grained varieties of lump
graphite that are easily reduced to fine
particle size by grinding are called
amorphous lump to distinguish them from
the tough, platy and acicular varieties,
known as crystalline lump, that can be
reduced in particle size only with extreme
difficulty.
Crystalline flake graphite is well
defined in paragraph 214 of the Tariff
Act of 1930 as follows:
"The term crystalline flake means
graphite, or plumbago, which occurs
disseminated as a relatively thin flake
throughout   its  containing  rock,
decomposed or not, and which may or
has been separated therefrom by ordinary
crushing, pulverizing, screening, or
mechanical concentration process, such
flake being made up of a number of
parallel laminae, which may be separated
by mechanical means."
Under the foregoing definition, finely
divided particles of crystalline flake
graphite would be classified as crystalline
graphite.  The   Court of Customs
Appeals, however, has held that
commercial designations and not scientific
terms must govern classification, and
when a commercial meaning differs from
the technical meaning, the commercial
designation must govern.  Therefore,
quantities of fine crystalline flake graphite
are imported under the amorphous
classification.
Sri Lankan lump graphite is classified
as amorphous or crystalline. Each type is
divided into a number of grades,
depending on the size (such as lump,
ranging from the size of walnuts to that
of peas; chip, from that of peas to about
that of wheat grains; and dust, finer than


60 mesh), graphitic carbon content, and
degree of consolidation.
Amorphous graphite is graded
primarily on graphitic carbon content.
Commercial ore contains about 75% to
93 % carbon, depending on the source.
Crystalline flake graphite from
Madagascar is divided into two main
grades, "flake" (coarse flake) and "fines"
(fine flake). Madagascan crucible flake
must have a minimum of 85% graphitic
carbon and be essentially all minus 20
plus 80 mesh in particle size. Other
crystalline flake graphites are also graded
according to graphitic carbon content and
particle size.
Natural graphite is marketed in the
form of crystalline graphite as flake,
lump, chip, and dust and in the form of
amorphous graphite in sizes from fine
powder to lumps up to the size of
walnuts. It is common practice to blend
different graphite to obtain a product
having certain desired physical and
chemical properties. In many instances,
the composition of these blends is
retained as a trade secret.
Geology-Resources
The three principal types of natural
graphite-lump, amorphous, and
crystalline flake-are based on physical
characteristics that are the result of major
differences in geologic origin and
occurrence. A variety of silicate minerals
are generally associated with graphite in
the ore.
Lump graphite occurs as fissure-filled
veins. It is typically massive, ranging in
particle size from extremely fine grains
(amorphous) to coarse, platy intergrowths


419


GRAPHTE-1993




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