Thorite
Current inventory: 0 gems
 

  
Thorite is named for its chemical composition containing thorium, a highly radioactive element, which was named for Thor, the Scandinavian god of war.

Discovered in 1829; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

(Th,U)SiO₄

Thorium Uranium Silicate

Molecular Weight:

324.12 gm

Composition:

Thorium

71.59 %

Th

81.46 %

ThO₂

Silicon

8.67 %

Si

18.54 %

SiO₂

Oxygen

19.74 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/A.09-30

Nickel-Strunz 10th Ed. ID:

9.AD.30

9 : SILICATES (Germanates)
A : Nesosilicates
D : Nesosilicates without additional anions; cations in [6] and/or greater coordination

Related to:

Zircon Group. The thorium analogue of Zircon and Hafnon. Dimorphous with Huttonite.

Members of Group:

Zircon Group: Hafnon, Stetindite, Thorite, Thorogummite, Zircon

Varieties:

Auerlite, Calciothorite, Ferrithorite, Gel-Thorite, Hydroauerlite, Mozambikite, Orangite, Uranohydrothorite, Uranothorite, Yanshainshynite

Synonyms:

Eukrasite, Torite

Crystal Data

Crystallography:

Tetragonal - Ditetragonal Dipyramidal

Crystal Habit:

Crystals typically square prisms, terminated by {111}, or pseudo-octahedral crystals, to 8 cm; also massive and compact

Twinning:

None

Physical Properties

Cleavage:

Distinct on {110}

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

4.5 - 5.0

Density:

4.00 - 6.70 (g/cm³)

Luminescence:

None

Radioactivity:

Very Strong; GRapi = 1,281,657.29 (Gamma Ray American Petroleum Institute Units)

Health Warning:

Contains thorium and uranium - always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest. Avoid prolonged exposure in proximity of the body. Store away from inhabited areas.

Optical Properties

Color:

Orange, Yellow-Orange, Brownish Yellow, Brownish Black, Black

Transparency:

Opaque to Subtranslucent; transparent in thin fragments

Luster:

Resinous, Greasy, Dull

Refractive Index:

1.78 - 1.84  Uniaxial ( + ) (metamict)

Birefringence:

0.010 - 0.020

Dispersion:

n/a

Pleochroism:

None

Occurances

Geological Setting:

An accessory mineral in felsic igneous rocks and their associated pegmatites. As a detrital mineral in sediments.

Common Associations:

Zircon, Monazite, Gadolinite, Fergusonite, Uraninite, Yttrialite, Pyrochlore

Common Impurities:

Al, Fe, Pb, Ca, P, Ti, REE, Y, Mg, H₂O

Type Locality:

Løvøya (Løvø; Lövö), Langesundsfjorden, Porsgrunn, Telemark, Norway

Year Discovered:

1829

View mineral photos:

Thorite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Thorite is an extremely rare gem and is highly radioactive. It is a member of the Zircon Group of minerals that includes Coffinite, Thorite and Zircon among others. Thorite is rarely found as crystals but normally found in massive form. Although Thorite contains about 72% thorium and is the most common thorium mineral, it is not the primary ore of thorium. The phosphate mineral Monazite only contains about 6% thorium but is mined in sufficient quantities to supply most of the current thorium demand. Thorite is an important ore of uranium. Because Thorite is highly radioacitve, it is often metamict. Metamict is the process in radioactive minerals of the destruction of the mineral's internal crystal lattice by its own radioactivity. This process can completely destroy the crystal lattice while leaving the outward appearance unchanged.

Thorite is mainly for collectors of rare and unusual gems, black gems or radioactive gems. Thorite is a highly radioactive mineral and should be stored away from other minerals and gems that might be damaged by radioactivity. Human contact and exposure to Thorite mineral specimens or gems should be limited!

Distribution: In Norway, from Lomo, Brevik, and around the Langesundsfjord; at Ødegården, Bamble; also Arendal, Tvedestrand, Kragerö, and elsewhere. From Mendig, Eifel district, Germany. In Madagascar, at Ambatofotsy, Androtsabo, Befaritra, and elsewhere. In the USA, from the Baringer Hill pegmatite, 26 km west of Burnet, Llano County, Texas; at St. Peters Dome, near Pikes Peak, El Paso County, and the Powderhorn district, Gunnison County, Colorado; from the Wet Mountains, Custer County, Colorado. In Canada, as large but crude crystals from the McDonald mine, Hybla, and at Wilberforce, Ontario. Additional minor localities are known.
 

  
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