Mineral Facts and Problems: 1960 Edition Page: 98
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MINERAL FACTS AND PROBLEMS, ANNIVERSARY EDITION
size for concentrating minerals such as feld-
spar and mica. Where conditions warrant,
mechanized mining methods are used.
MILLING
Beryl, feldspar, and some other pegmatite
minerals have densities so nearly the same that
it is difficult to separate beryl by mechnical
methods. Flotation methods have produced
beryl concentrates on a laboratory scale, but
in the past it has been difficult to produce ma-
terial on a commercial scale to equal the quality,
price, and ease of obtaining hand-sorted beryl.
Consequently, all commercial beryl is hand-
cobbed, and seldom are crystals and fragments
recovered that are less than 1 inch in size.
Probably not more than one-third of the beryl
in the average commercial deposit is recovered
by the crude hand methods now employed.
PREPARATION OF BERYLLIUM OXIDE AND BERYLLIUM
Although several methods for converting
beryl to beryllium oxide have been developed,
only two methods are used commercially in the
United States. These are the Copaux-Kawecki
fluoride process, used by The Beryllium Corp.,
and the Sawyer-Kjellgren Sulfate process, used
by The Brush Beryllium Co. (2, 4, 13).
In the Copaux-Kawecki fluoride process
beryl containing from 10 to 12 percent BeO is
crushed and ground in a wet ball mill until
about 90 percent is minus-200-mesh. It is then
mixed with soda ash, sodium silicofluoride, and
sodium ferric fluoride and made into briquets.
The briquets are sintered, cooled, crushed, and
ground in a rubber-lined wet pebble mill, and
the slurry is pumped to tanks. More water at
room temperature is added and the mixture
agitated, leached, and allowed to settle. The
liquid, containing soluble sodium beryllium
fluoride, is decanted to separate it from the
solids, which contain aluminum and iron oxides
and silica. Caustic soda is added to the solu-
tion to precipitate beryllium hydroxide, which
is filtered, washed, dried, and ignited at about
8000 C. to convert it into beryllia, BeO. The
sodium fluoride remaining in the filtrate is
recovered by adding ferric sulfate to form a
precipitate of sodium ferric fluoride or iron
cryolite, which is separated by filtration and
used again for sintering more beryl.
The Sawyer-Kjellgren process is based on the
discovery that if melted beryl is quenched in
cold water the resultant frit reacts with sul-
furic acid. The beryl, containing 10 to 12 per-
cent beryllia, is crushed, dried, and melted in
an electric are furnace. The melted beryl is
poured into water to obtain frit, which is dry-
ground in a ball mill to a fine powder. Batches
of the powder are mixed with concentrated sul-
furic acid, steamed, and agitated. Water and
more steam are then added to the slurry. Theliquid, containing soluble beryllium and alumi-
num sulfates, is filtered from the sediment and
pumped to a tank where ammonium hydroxide
is added. The filtrate from this operation is
further treated with a chelating agent to pre-
vent impurities from precipitating upon sub-
sequent addition of caustic soda. Hydrolysis
follows, and the precipitate, beryllium hydrox-
ide, is filtered off. This precipitate is ignited
in an electric furnace to form beryllium oxide.
The berylliumproducts of either the Copaux-
Kawecki or the Sawyer-Kjellgren process gen-
erally have to be purified to produce the metal.
The oxide or hydroxide can be dissolved in
ammonium bifluoride solution and heated to
boiling, and calcium carbonate flour is added
to precipitate aluminum (13). Lead dioxide is
added to remove manganese and chromium, and
the resultant slurry is filtered through pressure
filters using stainless-steel screens precoated
with rayon fiber. Lead, nickel, and copper are
next removed from the filtrate with ammonium
polysulfide. After being filtered again, the
solution is evaporated, and pure ammonium be-
ryllium fluoride is recovered by crystallization.
This fluoride is then thermally decomposed to
beryllium fluoride, while the ammonium fluo-
ride is volatilized.
Beryllium metal is produced by the reduction
of beryllium fluoride with magnesium metal.
This is usually done in batches in a high-fre-
quency induction electric furnace provided with
a graphite crucible (2, 4, 13). An excess of
beryllium fluoride must be used to keep the high-
ly exothermic reaction under close control.
When reduction of the batch has been completed
the temperature is raised to about 1,3000 C. to
melt the beryllium and allow it to coagulate into
a pool at the surface of the slag. After cooling,
the solid beryllium is separated from the slag,
and the slag is leached to recover its beryllium
content. The metal is remelted in a vacuum,
which volatilizes slag occlusions and small
amounts of impurities such as magnesium.
PREPARATION OF BERYLLIUM-COPPER MASTER ALLOY
Weighed quantities of beryllium oxide, car-
bon powder, and copper powder or copper oxide
are mixed in batches and melted in an electric
arc furnace (2). The product is impure beryl-
lium copper. Additional refining or other
treatment removes the carbon and gases ab-
sorbed during reduction. The final product,
which contains about 4 percent beryllium, is
called beryllium-copper master alloy.
USES
In recent years considerable interest in beryl-
lium has developed in the fields of nuclear en-
ergy and supersonic aircraft, missiles, and space
vehicles.98
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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/m1/106/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.