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Thorite
Mineral Facts:
Chemical
Formula: ThSiO4
Thorium
silicate, always with some water, probably from alteration, and sometimes
uranium.
Colors:
It is black
or orange-yellow.
Hardness:
4.5 to 5
Density:
4.5-5 for black varieties and 5.2-5.4 for the orange varieties.
Cleavage:
Two poor cleavages in
prismatic form.
Crystallography:
Tetragonal
Crystal forms resemble
those of zircon. It also occurs in massive forms.
Luster:.
Resinous to greasy luster. Transparent to opaque.
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Composition, Structure and
Associated Minerals:
The mineral
occurs as a constituent of the igneous rock,
augite-syenite, at several points in the neighborhood
of the Langesundfjord, Norway, Because thorite is highly
radioactive, dark, opaque specimens are often metamict. This is a condition found in
radioactive minerals caused by the destructive effects of its own
radiation on the mineral's crystal lattice.
Thorite is not
a common mineral, but specimens of thorite generally come from
igneous pegmatites, volcanic extrusive rocks, hydrothermal veins, contact
metamorphic rocks, and as small grains found in beach sands. Well formed crystals are
rare.
Identification
and Diagnostics
Its
streak is brown or light orange.
Hydrated specimens are soluble in hydrochloric acid
with the production of gelatinous silica. Infusible. Soluble in
hydrochloric acid
and gives gelatinous silica upon evaporation. A rare mineral, found
chiefly in Norway, commonly altered. Hydrated specimens are soluble in hydrochloric acid
with the production of gelatinous silica.
Because of the presence of the element Thorium
in Thorite, it is a highly
radioactive mineral.
Localities
Thorite has been found in small amounts at a number
of places. Well known
European localities include Arendal, Langesundfjord, Norway;
the Laach Lake Volcanic Complex, Eifel Mountains, Germany; the San Vito
Quarry, Monte Somma, Vesuvious, Italy; and Vetralla and Bassano Romano,
Viterbo Province, Italy. Other worldwide occurrences include Mogok, Burma
(Myanmar); Balangoda, Ratnapura, Sabaragamuwa province, Sri Lanka and Vorondolo, Fianarantsoa Province, Madagascar.
In Canada, Thorite comes from Ontario in the Bancroft District, Hastings
Co.; and from the Kemp Uranium Mine, Cheddar, Cardiff Township, Haliburton
Co., Ontario;. In the U.S., Thorite
specimens come from the the Thomas Range, Juab Co., Utah; Mount Rosa, El Paso
Co., Colorado; the Seerie
pegmatite, Jefferson Co., Colorado; and from the Barringer Hill, Llano
Co., Texas..
Industrial Uses of
Thorite
Thorite is actually an
important uranium ore. A special variety of thorite known as "uranothorite"
is rich in uranium and has been mined as a uranium ore at
Bancroft, Ontario, in Canada.
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