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Thorite Crystal

The Mineral thorite

Thorite is named for its content of the rare element thorium. It is isomorphous with Zircon and occurs in the same crystal habits. Thorite is the most prevalent mineral containing the radioactive element thorium. However, it is not as important as the primary thorium ore, Monazite, since the extraction process of the ore from Thorite is more difficult then that of Monazite.

Thorite, being radioactive, must be stored with all the precautions exercised with radioactive minerals. The radioactivity of Thorite often brings it to a state of metamiction, in which its crystal structure becomes unstable thereby causing the crystal edges to become smooth and rounded. When this happens, the Thorite may gain hydroxyl (OH) molecules in place of the silica (SiO4) molecules and transform into a different mineral, Thorogummite.
Chemical Formula ThSiO4
Since Thorite often contains considerable uranium, its formula may also be written as (Th,U)SiO4
Composition Thorium silicate, almost always with some uranium, and sometimes with zirconium, hafnium, and yttrium
Variable Formula (Th,U)SiO4 ;
Color Black, reddish-brown, brown, orange, orange-yellow, green
Streak Light brown
Hardness 4.5 - 5
Crystal System Tetragonal
Crystal Forms
and Aggregates
As stubby and prismatic crystals, which are usually terminated. Crystals are rarely as elongated prisms. Most often grainy, reniform, as fibrous masses, and massive. Crystals are usually rounded at the edges due to the metamict nature of Thorite caused by radioactivity.
Transparency Opaque. Rarely transparent.
Specific Gravity 4.0 - 6.7
Luster Resinous to pitchy
Cleavage 3,2
Fracture Conchoidal to splintery
Tenacity Brittle
In Group Silicates; Nesosilicates
Striking Features High specific gravity, luster, and strong radioactivity
Environment In rare earth granite pegmatites and pyroclastic volcanic deposits.
Rock Type Igneous
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 2


 -  Calcium-rich variety of Thorite.
 -  Orange variety of Thorite.
 -  Highly radioactive replacement pseudomorph of Thorite that has hydroxyl (OH) molecules replacing some of the silica molecules. Though sometimes considered a variety of Thorite, it is classified as a unique mineral species.
 -  Uranium-rich variety of Thorite, containing up to half of the thorium replaced by uranium.

Thorite is an important ore of the radioactive element thorium.

Thorite is not a common mineral. 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); and Vorondolo, Fianarantsoa Province, Madagascar.

In Canada, Thorite comes from Ontario in the Bancroft District, Hastings Co.; and from the Kemp prospect, Cheddar, Haliburton Co. In the U.S., Thorite comes from the the Thomas Range, Juab Co., Utah; Mount Rosa, El Paso Co., Colorado; the Butterfield and Seerie pegmatites, Jefferson Co., Colorado; and from the Barringer Hill, Llano Co., Texas.

Quartz, Biotite, Orthoclase, Zircon, Monazite, Xenotime, Betafite

Carnotite and Tyuyamunite- Softer and lighter in weight.
Zircon and Hafnon - Harder, different streak.

thorite PHOTOS
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