content. Today, the term "metspar" is
usually used to refer to material with a
minimum content of 85 %, but is
sometimes used for material as high as
96 %, which includes what is technically
ceramic grade. Metspar is commonly
traded as lump or gravel that must meet
physical requirements similar to those of
the National Defense Stockpile purchase
specifications discussed below.
According to the current National
Defense Stockpile purchase specifications
(P-69b-R3), which were determined by
the Federal Interagency Committee for
Stockpile Purchase Specifications and
Special Instructions in consultation with
U.S. steel producers, metallurgical-grade
fluorspar must contain a minimum of
70% by weight effective CaF2.
Specifications for maximum allowable
impurities are as follows: sulfur =
0.10%, lead = 0.25%, arsenic -
0.01%, barium = 0.01%, zinc -
0.01%, phosphorus = 0.25%, tin -
0.02%, antimony = 0.02%, and copper
= 0.10 %. Physical requirements are that
all metallurgical-grade fluorspar shall be
in the form of gravel and, after washing,
shall pass a 75-millimeter (3-inch) sieve,
and not more than 10% by weight shall
pass a 9.5-millimeter (3/8-inch) sieve.
In the domestic steel industry, various
shapes and sizes of briquets or pellets are
being used. Generally made to consumer
specifications, briquets contain varying
quantities of fluorspar mixed with
binders, fillers, and fluxing agents.
Typically made on roll presses and
ranging in size from that of a peach seed
to a 5-centimeter square, briquets contain
25% to 90% CaF2 and steel mill waste
ingredients, such as mill scale, flue dust,
shredded scrap, iron ore fines, and
manganese ore fines. The most popular
binders are molasses and lime, which do
not require baking ovens.  Imported
briquets are often made from fines
accumulated during metspar preparation
and from flotation concentrates. Pellets
have been made on balling machines
using sodium silicate binder.
Geology-Resources'
Fluorspar occurs in a wide variety of
geological environments, which indicates


that deposition takes place in a number of
different ways.  From   an economic
standpoint, seven of the most important
modes of occurrence are as follows:
1. Fissure vein deposits commonly
occur along faults or shear zones and are
the most readily recognized form of
fluorspar occurrence in the world.
Although the vein structure may be
persistent, the fluorspar mineralization
commonly occurs as lenses or ore shoots
separated by barren zones. Fissure veins
occur in igneous, metamorphic, and
sedimentary rocks.
2. Stratiform, manto, or bedded
deposits occur  as  replacements in
carbonate rocks. Some beds are replaced
adjacent to structural features such as
joints and faults. Frequently, there is a
capping of sandstone, shale, or clay.
3. Replacement deposits in carbonate
rocks along the contact with acidic
igneous intrusives are another common
type of deposit. Deposits do not have to
be the result of contact metamorphism,
but may be introduced later, following the
contact zone as a conduit and replacing
the limestone.
4. Stockworks and fillings in shear and
breccia zones are another form in which
fluorspar occurs. The Buffalo deposit in
the Transvaal consists of a network of
fluorspar veinlets in sill-like bodies that
are inclusions in the granite of the
Bushveld complex.
S. Carbonatite and alkalic rock
complexes may have fluorspar at their
margins.   Fluorspar grades are not
usually sufficient to be economic, but the
Okorusu deposit in Namibia is made up
of a number of bodies of fluorspar in
limestones, quartzites, and related rocks
that   have   been   intruded   and
metamorphosed by an alkaline igneous
rock complex.
6. Residual deposits of fluorspar are
formed in clayey and sandy residuum that
results from surficial weathering of
fluorspar veins and replacement deposits.
These deposits may be the sources of
metallurgical-grade  fluorspar.  They
include detrital deposits blanketing the
apex of veins and the upper portions of
the veins themselves that have been
weathered to depths of 30 meters or
more.


7. Fluorspar also may occur as a
major gangue mineral in lead and zinc
vein deposits. Two operations in the
Parral area of Mexico have treated the
tailings of lead-zinc mines to recover
fluorspar from previously discarded
gangue minerals.
Identified world fluorspar resources
are approximately 430 million tons of
contained fluorspar.  As might be
expected, the countries with the highest
production have the largest fluorspar
reserves,  although  their production
ranking does not necessarily mirror their
reserve ranking.  World resources of
equivalent fluorspar from phosphate rock
are approximately 325 million tons,
which includes about 32 million tons
from domestic phosphate rock.
Technology
Mining.2-Mining   methods   vary
according to geologic conditions at
individual deposits around the world.
Deep    deposits  usually   require
underground techniques, while wide,
shallow deposits employ open pit
methods. If the ground is unable to
support underground mining, open pit
methods may be used even though
overburden removal might be substantial.
In some cases, open pit methods are used
until the mining reaches a practical
production limit because of excessive
waste removal. Mining operations then
move underground.
Narrow vein mining is commonly done
by shrinkage stoping and open stoping
where strong walls occur, while
stratiform or bedded deposits use room-
and-pillar patterns.  Replacement and
fissure vein deposits are mined with
shrinkage stoping or cut-and-fill methods
if they are deep, narrow occurrences.
They also may be mined by open pit or
strip-mining techniques when they occur
near the surface and have competent
sidewalls.   The   replacement  and
stockwork deposits in the Republic of
South Africa, the carbonatite deposit in
Namibia, and most of the fissure veins in
Thailand are mined with open pit
methods. However, replacement deposits
in Mexico are extracted by stoping or cut-
and-fill methods.


3FLUORSPAR-1993








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