Thorianite
Current inventory:  0 gems
 

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

Discovered in 1904;   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

ThO₂

Thorium Oxide

Molecular Weight:

264.04 gm

Composition:

Thorium

87.88 %

Th

100.00 %

ThO₂

Oxygen

12.12 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.31-50

Nickel-Strunz 10th Ed. ID:

4.DL.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
L : With large (+- medium-sized) cations; fluorite-type structures

Related to:

Thorianite-Uraninite Series.

Varieties:

Aldanite, Uranothorianite

Synonyms:

α-Thorianite, β-Thorianite, γ-Thorianite, Uraninitte (of Coomaraswamy)

Crystal Data

Crystallography:

Isometric - Hexoctahedral

Crystal Habit:

Cubic crystals, rarely modified by {111} and {113}, to 9 cm, usually rounded to some degree (water worn)

Twinning:

Penetration twins on {111} very common

Physical Properties

Cleavage:

Poor on {001}

Fracture:

Irregular/Uneven to Sub-Conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.5 - 7.0

Density:

9.70 - 9.80 (g/cm³)

Luminescence:

Radioactive

Radioactivity:

Very Strong; GRapi = 1,505,305.18 (Gamma Ray American Petroleum Institute Units)

Health Warning:

Contains thorium - 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:

Black, brownish black, dark gray, dark reddish brown, may have a bronzy tarnish; in transmitted light, dark brown, reddish brown, greenish; gray with red-brown internal reflections in reflected light.

Transparency:

Opaque; Transparent in very thin fragments

Luster:

Submetallic when fresh, altering to Resinous

Refractive Index:

2.20 - 2.35  Isotropic; may show anomalous anisotropism

Birefringence:

0.000;  Isotropic

Dispersion:

n/a

Pleochroism:

n/a

Anisotrophism:

May show anomalous anisotropism; red-brown internal reflections in reflected light.

Occurances

Geological Setting:

An accessory mineral in granite pegmatites, more rarely in carbonatites or serpentinites; commonly detrital in heavy mineral concentrates.

Common Associations:

Thorite, Zircon, Ilmenite, Cassiterite, Allanite (Sri Lanka); Phlogopite, Diopside, Spinel (Andolobe, Madagascar)

Common Impurities:

U, Ce, La, Pb, TR

Type Locality:

Balangoda, Ratnapura, Sabaragamuwa Province, Sri Lanka

Year Discovered:

1904

View mineral photos:

Thorianite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Thorianite is a rare thorium oxide mineral that is strongly radioactive due to its throium content. It is more stongly radioactive than Thorite, another thorium mineral that contains both thorium and uranium. Thorium was originally discovered by Ananda Coomaraswamy in 1904 as Uraninite, but recognized as a new species by Wyndham R. Dustan. Thorianite is a rare mineral, but an even rarer as a faceted gem. Thorianite is usually black with a submetallic luster and Mohs hardness of 6.5 - 7.0.

Thorianite is mainly for collectors of rare and unusual gems, black gems or radioactive gems. Thorianite 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 Thorianite mineral specimens or gems should be limited!

Current sources are Balangoda, Ratnapura, Sabaragamuwa Province, Sri Lanka; Betroka, Madagascar, where very large crystals are found; and other locations including South Africa, Russia, USA and Canada.
 

  
Thorianite gems for sale: