Thorite

Thorite
Thorite crystal from the Kemp uranium mine in Ontario (size: 2.2 x 2.2 x 1.6 cm)
General
CategorySilicate mineral
Formula
(repeating unit)
(Th,U)SiO4
IMA symbolThr[1]
Strunz classification9.AD.30
Crystal systemTetragonal
Crystal classDitetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)
Space groupI41/amd
Unit cella = 7.13, c = 6.32 [Å]; Z = 4
Identification
ColorYellow-orange, brownish yellow, brownish black, black, green
Crystal habitIn square prisms, or pseudo-octahedral crystals; also massive
CleavageDistinct on {110}
FractureConchoidal
TenacityBrittle
Mohs scale hardness4.5 – 5
LusterVitreous to resinous
StreakLight orange to light brown sometimes even an alien magenta
DiaphaneityNearly opaque, transparent in thin fragments
Specific gravity6.63 – 7.20
Optical propertiesUniaxial (−)
Refractive indexnω = 1.790 – 1.840 nε = 1.780 – 1.820
Birefringenceδ = 0.010 – 0.020
Alters toCommonly metamict
Other characteristics Radioactive
References[2][3][4]

Thorite, (Th,U)SiO4, is a rare nesosilicate of thorium that crystallizes in the tetragonal system and is isomorphous with zircon and hafnon. It is the most common mineral of thorium and is nearly always strongly radioactive. Thorite was discovered in 1828 on the island of Løvøya, 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 its thorium content.

  1. ^ 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. S2CID 235729616.
  2. ^ Webmineral data
  3. ^ Mindat.org
  4. ^ Handbook of Mineralogy
  5. ^ Berzelius, M. (1829). "Thorite, a new mineral, and thorina, a new earth". Philosophical Magazine. Series 2. 6 (35): 392–393. doi:10.1080/14786442908675174.
  6. ^ 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.
  7. ^ Marshall, J.L.; Marshall, V.R. (2001). "Rediscovery of the Elements- Thorium-Løvøya, Langesundsfjord, Norway" (PDF). The Hexagon. 93: 70–73. Archived from the original (PDF) on 2005-04-08.