Thorite
| Thorite | |
|---|---|
 Thorite crystal from the Kemp uranium mine in Ontario (size: 2.2 x 2.2 x 1.6 cm) | |
| General | |
| Category | Silicate mineral |
| Formula (repeating unit) | (Th,U)SiO4 |
| IMA symbol | Thr[1] |
| Strunz classification | 9.AD.30 |
| Crystal system | Tetragonal |
| Crystal class | Ditetragonal dipyramidal (4/mmm) H-M symbol:(4/m 2/m 2/m) |
| Space group | I41/amd |
| Unit cell | a = 7.13, c = 6.32 [Å]; Z = 4 |
| Identification | |
| Color | Yellow-orange, brownish yellow, brownish black, black, green |
| Crystal habit | In square prisms, or pseudo-octahedral crystals; also massive |
| Cleavage | Distinct on {110} |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scalehardness | 4.5 – 5 |
| Luster | Vitreous to resinous |
| Streak | Light orange to light brown sometimes even an alien magenta |
| Diaphaneity | Nearly opaque, transparent in thin fragments |
| Specific gravity | 6.63 – 7.20 |
| Optical properties | Uniaxial (−) |
| Refractive index | nω= 1.790 – 1.840 nε= 1.780 – 1.820 |
| Birefringence | δ = 0.010 – 0.020 |
| Alters to | Commonly metamict |
| Other characteristics |  Radioactive |
| References | [2][3][4] |
Thorite,(Th,U)SiO4,is a rarenesosilicateofthoriumthatcrystallizesin thetetragonalsystem and isisomorphouswithzirconandhafnon.It is the most commonmineralofthoriumand is nearly always stronglyradioactive.Thorite was discovered in 1828 on the island ofLøvøya,Norway, by the vicar and mineralogist,Hans Morten Thrane Esmark.First specimens of Thorite were sent to his father,Jens Esmark,who was a professor of mineralogy and geology.[5][6][7]It was named in 1829 to reflect itsthoriumcontent.
Occurrence
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Specimens of thorite generally come fromigneouspegmatitesandvolcanicextrusive rocks, hydrothermal veins and contactmetamorphic rocks.It is also known to occur as small grains in detrital sands. Crystals are rare, but when found can produce nicely shaped short prismatic crystals with pyramidal terminations. It is commonly associated withzircon,monazite,gadolinite,fergusonite,uraninite,yttrialiteandpyrochlore.[4]
Thorite is currently an important ore ofuranium.A variety of thorite, often called "uranothorite", is particularly rich in uranium and has been a viable uranium ore at Bancroft inOntario,Canada. Other varieties of thorite include "orangite", an orange variety, and "calciothorite", an impure variety with trace amounts ofcalcium.
Properties
[edit]Due to the radioactive elements contained, Thorite is commonlymetamict.With the destructive effects of radioactivity on thecrystal lattice,hydrated specimens are oftenamorphousand optically isotropic. Owing to differences in composition, thespecific gravityvaries from 4.4 to 6.6 g/cm3.Hardness is 4.5 and the luster is vitreous or resinous. The color is normally black, but can range from brownish black to orange, yellowish-orange and dark green.
References
[edit]- ^Warr, L.N. (2021)."IMA–CNMNC approved mineral symbols".Mineralogical Magazine.85(3): 291–320.Bibcode:2021MinM...85..291W.doi:10.1180/mgm.2021.43.S2CID235729616.
- ^Webmineral data
- ^Mindat.org
- ^abHandbook of Mineralogy
- ^Berzelius, M. (1829)."Thorite, a new mineral, and thorina, a new earth".Philosophical Magazine.Series 2.6(35): 392–393.doi:10.1080/14786442908675174.
- ^Berzelius, J. J. (1829)."Untersuchung eines neuen Minerals und einer darin enthaltenen zuvor unbekannten Erde".Annalen der Physik und Chemie.92(7): 385–415.Bibcode:1829AnP....92..385B.doi:10.1002/andp.18290920702.
- ^Marshall, J.L.; Marshall, V.R. (2001)."Rediscovery of the Elements- Thorium-Løvøya, Langesundsfjord, Norway"(PDF).The Hexagon.93:70–73. Archived fromthe original(PDF)on 2005-04-08.
External links
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