Mineral Facts and Problems: 1960 Edition Page: 63
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London, E. C. 3, England; and Mitsui & Co.,
Ltd., Central Post Office Box 97, Tokyo, Japan.
Chemical grade ore is that which has a pur-
ity sufficient to justify its direct use in produc-
tion of the oxide, chloride, and other industrial
chemical compounds. To qualify as Chemical
grade, an ore must have no single metallic im-
purity greater than 0.1 percent and maximum
combined metallic impurities of 0.25 percent.
Liquated antimony sulfide, variously termed
"crudum," "crude antimony," or "needle anti-
mony," is marketed on a basis of 70 percent an-
Generally, antimony deposits are small, dis-
continuous bodies having relatively simple ge-
ologic relations. Stibnite (Sb2Ss), together
with its oxidized equivalents, is the principal
ore mineral. It is found with a limited suite of
silicate and carbonate gangue minerals in fis-
sure veins and replacement bodies. The depos-
its are apparently hydrothermal in origin.
Common genetic associations are with granites,
grandodiorites, and monzonites; however, the
enclosing rock walls may be any type traversed
by the mineralizing fluids during the ore-form-
ing process. The mineralogy of the veins and
their almost invariable shallow depth suggest a
low temperature of formation at near-surface
positions, possibly related to the configuration
of the water table at the time of deposition.
Most of these geologically simple stibnite de-
posits do not contain more than several thou-
sand tons of ore; nevertheless, the world's most
productive antimony mines, including those of
Mexico, Bolivia, China, Peru, Yugoslavia, and
Algeria are of this type. The economics of
their production is often related to (1) minor
recoverable values of other ore constituents and
(2) locally low mining and transportation
costs unrelated to the inherent nature of the
Antimony also occurs as a constituent of
other metalliferous ores. This category ranges
in complexity from rather simple deposits in
which stibnite is a significant segment of
quartz-gold veins to copper-lead-zinc sulfide
bodies, in which minor antimony occurs locked
within a complex crystal lattice such as tetra-
hedrite. Virtually all domestic mine output
has been from these more complex deposits. In
some ore bodies the antimony content shares
the total value equally with one or more other
metallic constituents of the ore. In many de-
posits the antimony content of the ore is so
small that its presence is detected at some stage
in processing so far removed from the mining
operation that identity and quantitative rela-
tion to specific ore bodies is obscure.
DEVELOPMENT, MINING, MILLING, AND SMELTING
Because of the geologic configuration of a
typical antimony deposit, entry is by a shallow
shaft or short adit, development by sill cutting
in the plane of the vein, and stoping by simple
overhand methods between raises driven on the
footwall of the ore.
A large-tonnage open-pit mine near Stibnite,
Idaho containing disseminated value in gold,
antimony, and tungsten was in production be-
fore 1953, demonstrating that antimony mining
need not be totally confined to small-scale un-
Commercial ores range from low grades, con-
taining only 1 or 2 percent antimony, to high
grades that approach the theoretically pure
limit of stibnite, 71.5 percent antimony. The
lower grade ores are hand sorted or milled by
flotation or simple tabling methods. Owing to
friability of stibnite, jigging and dense-me-
dium processes entail prohibitively high slime
Ores and residues containing 5 to 25 percent
antimony may be treated directly by roasting
to yield the volatile trioxide or the stable, non-
volatile tetroxide. Temperature and quantity
of available oxygen determine the kind and
relative quantity of the oxide produced. Vola-
tilization roasting may be conducted as an ore
concentrating and intermediate smelting proc-
ess or as a refining method for producing a
commercially marketable end product.
Ores containing 45 to 60 percent antimony
often are liquated to increase the Sb2S3 content,
to free the antimony sulfide from associated
gangue, and/or to make a directly marketable
product. The ore or concentrate is heated in a
crucible or reverberatory furnace to a point
above the melting point but maintained below
the volatilization temperature of stibnite. The
fused sulfide descends by gravity through the
ore mass and is tapped and collected in a lower
container. The resulting material, termed
"crudum" or "crude antimony," is used directly
in many military and industrial processes.
Antimony metal, termed "regulus," is recov-
ered from the trioxide and tetroxide produced
in volatilization and dead roasting, from liq-
uated sulfide, from intermediate grades of ores
by direct smelting, and from slags and residues
produced in refining other metals such as lead.
Oxides are reduced most conveniently in rever-
beratory furnaces, using coke and a suitable
flux such as soda ash.
Rich sulfide ore and crudum are reduced to
metal by iron precipitation in some localities,
as in England, Hungary, Japan, and Mexico.
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United States. Bureau of Mines. Mineral Facts and Problems: 1960 Edition, report, 1960; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc38790/m1/71/: accessed October 18, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.