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Diaspore
Mineral Facts:
Chemical
Formula: AlO(OH)
Diaspore is
a hydrated oxide of aluminum. It is a valuable ore of the metal. Analyses
normally show it to contain some iron and silicon impurities.
Colors:
White, gray, yellowish, greenish, pink.
The
tint is always light and the streak colorless.
Hardness:
6.5
to 7
Density:
3.35 to 3.45
Cleavage:
One perfect cleavage
parallel to brachypinacoid.
Crystallography:
Orthorhombic
Usually in thin
crystals, but also in foliated masses and in stalactitic forms.
Luster:.
Vitreous luster except on cleavage faces, where it
is pearly. The mineral is transparent or translucent.
Optics:
(Refractive Index): = a
= 1.702, b=1.722, y=1.750. |
Diaspore Aluminum ore |
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Composition, Structure and
Associated Minerals:
Diaspore occurs as crystals
that are a decomposition product of
corundum and other minerals, and on the walls of rocks in which corundum
is found. It is probably in most cases a decomposition product of other
aluminum bearing minerals.
Usually found associated with that mineral in
dolomite, chlorite-schist, etc. The name is derived from a Greek word
meaning to scatter, in allusion to its violent decrepitation when heated.
Identification
and Diagnostics
It is infusible and insoluble in the normal acids.
Fine powder wholly soluble in
salt of phosphorus bead (absence of silica).
When moistened with a solution of cobalt nitrate and heated it turns blue,
as do all other colorless aluminum compounds
(test for aluminum).
In the closed tube diaspore decrepitates and gives off water at a high
temperature. In appearance, diaspore closely resembles
brucite (Mg(OH)2), from which it may be distinguished by its greater
hardness and its aluminum reaction with cobalt nitrate.
Characterized by its good cleavage,
scaly structure and its hardness (6.5-7).
Localities
It is an essential part of the aluminum ore bauxite, and is found as a part
of all bauxite deposits.
Fine clear, gem quality crystals
come from Turkey.
In Ekaterinburg, Russia, it is associated with emery. At Schemnitz, Hungary,
it occurs in veins. It is found also in the Canton of Tessin, as well as at
Campolongo
in Switzerland, at various places in Asia Minor, and on the emery-bearing
islands of the Grecian Archipelago. In the United States it is associated
with
corundum, at Newlin, Chester Co., Penn., with emery at
Chester, Massachusetts;
at the Culsagee corundum mine, near Franklin,
North Carolina,
and at other corundum mines in the same State.
Industrial Uses of
Diaspore
In combination with gibbsite and boehmite,
diaspore is one of the major components of the aluminum ore
bauxite, which is mined and processed in huge amounts around the world.
It is there fore an important aluminum ore.
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