Thorianite

Thorianite ( chemically: thorium dioxide ) is a rarely occurring mineral from the mineral class of oxides and hydroxides. It crystallizes in the cubic crystal system with the chemical composition and ThO2 usually develops cubical crystals rarely show that also at the corners of the octahedron. Thorianite from river sediments can have a very inconspicuous appearance against. Your matt washed- gloss would more likely resemble the polished black stones. Only the density and radioactivity is in such cases that it is not an ordinary stone.

Thorianite makes a perfect mixed batch with uraninite. Due to the good miscibility of both the thorium minerals may be in any ratio replaced by uranium.

Special Features

Thorianite is classified as highly radioactive due to its thorium content of up to 88% and has a specific activity of about 39.4 kBq / g (compared to natural potassium 31.2 Bq / g). Despite their high radioactivity resist Thorianite the Isotropierung, ie the metamikten destruction of the crystal lattice by its own radiation better than most other uranium and thorium containing minerals.

Its melting point is 3390 ° C with unusually high, although contaminated pieces partially have greatly differing melting points.

The mineral is diamagnetic, and thus has a tendency to migrate out of a magnetic field.

Etymology and history

Was first found thorianite 1904 at Balangoda ( Sabaragamuwa Province ) in Sri Lanka and described by Wyndham R. Dunstan, who named the mineral after its thorium content.

Classification

In the old ( 8th edition ) and new classification of minerals according to Strunz ( 9th edition ) of the thorianite belongs to the department of " oxides with the molar ratio of metal: oxygen = 1: 2". The 9th edition of Strunz'schen systematics divided this department but now more precisely according to the size of the cations involved as well as the crystal structure and the mineral is " with large (± medium-sized ) cations and fluorittypischen structures " to find accordingly in the subdivision.

The classification of minerals according to Dana sorted the thorianite also in the class of oxides, there, however, in the subdivision of " uranium and thorium oxides with a cation charge of 4 and of the general formula ( AO2 ) ".

Modifications and varieties

Uranothorianit is the uranium-rich variety of the Thorianits.

Education and Locations

Thorianite rarely forms large deposits. Usually it forms isolated crystals and more rarely small groups of crystals in pegmatites and certain metamorphic deposits. In natural weathering and erosion of the bedrock, the relatively resistant crystals are transported away and can accumulate in alluvial deposits (called, among other soaps).

One of the most famous localities for uranium thorianite (so-called Uranothorianit ) is Esiva in the Toliara Province ( Tulear ) in Madagascar, where he was present in crystals up to 2.5 cm in size.

Worldwide thorianite was at 124 localities demonstrated (as of 2009), so among other things in Badakhshan in Afghanistan; in the northeastern to eastern desert by the Red Sea in Egypt; Tasmania and Victoria in Australia; Minas Gerais and Pará in Brazil; Hebei, Jiangxi and Liaoning in China; at Kruft and Mendig (Eifel ) in Germany; at Narsaq in Greenland; several provinces of Italy; Nunavut, Ontario and Quebec in Canada; Chöwsgöl Aimag ( Hövsgöl ) in Mongolia; Alto Ligonha in Mozambique; Akershus Aust- Agder and Telemark in Norway; Eastern Siberia, the Urals and Kola in Russia; Småland in Sweden; in Košice in Slovakia; Spanish Catalonia; at Phalaborwa and Sutherland (South Africa ); Moravia in the Czech Republic; Fejér and Tolna in Hungary; as well as many regions of the United States.

Crystal structure

Thorianite crystallizes in the cubic crystal system in the space group F m3m with the lattice parameters a = 5.5997 Å and four formula units per unit cell, so it has a crystal structure similar to that of fluorite.

Use

Thorianite is rarely used alone for the extraction of thorium because of its usually low enrichment. This is also due to the current low demand for thorium. Therefore thorianite is rarely conveyed to the thorium extraction. Uranothorianite be promoted sporadically mainly for uranium mining. Along with other minerals ( monazite, etc.), the promotion already worth more. The Uranothorianit from Madagascar until the beginning of the 70 end of the 50 mined primarily for uranium mining. Currently ongoing exploration work ( deep wells ) have shown that a Uranothorianit mineralization can also pursue more in depth further ( shown in November 2007 to about 80 m with core drilling ).

Precautions

After each contact, it is advisable to wash your hands. It is sensible to storage in provided for collectors purposes transparent plastic boxes especially in small pieces. From purchasing large quantities of small loose pieces as they are partially available, it is not advisable because of the formation of dust and large range of the radiation. Smaller individual pieces in normal amounts, however, are of less concern.