Tyuyamunite

Tyuyamunite (pronounced tuh-YOO-ya-moon-ite) is a very rare uranium mineral with formula Ca(UO2)2V2O8·(5-8)H2O. It is a member of the carnotite group. It is a bright, canary-yellow color because of its high uranium content. Also, because of tyuyamunite's high uranium content, it is radioactive.[6] It was named by Konstantin Avtonomovich Nenadkevich, in 1912, after its type locality, Tyuya-Muyun, Fergana Valley, Kyrgyzstan.[3]

Tyuyamunite
General
CategoryVanadate mineral
Formula
(repeating unit)
Ca(UO2)2V2O8·(5-8)H2O
IMA symbolTyu[1]
Strunz classification4.HB.25
Dana classification40.2a.26.1
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPnna
Unit cella = 10.63 Å, b = 28.36 Å
c = 20.4 Å; Z = 4
Identification
ColourCanary yellow, lemon-yellow; greenish yellow (upon exposure to sunlight)
Crystal habitPlaty crystals often in radiating sprays, coatings, massive
CleavagePerfect on {001}, micaceous; distinct on {100} & {010}
Mohs scale hardness1+12 - 2
LustreAdamantine, waxy, pearly on {101}, dull
StreakYellow
DiaphaneityTranslucent to opaque
Specific gravity3.57 - 4.35
Optical propertiesBiaxial (-)
Refractive indexnα = 1.675 nβ = 1.860 - 1.870 nγ = 1.885 - 1.895
Birefringence0.210 - 0.220
Pleochroismweak: X = nearly colourless, Y = pale canary yellow, Z = canary yellow
2V angle30° to 45°
Dispersionnone
Other characteristics Radioactive
References[2][3][4][5]

Formation and transformation

Tyuyamunite is formed by the weathering of uraninite, a uranium-bearing mineral. Tyuyamunite, being a hydrous mineral, contains water. Yet when it is exposed to the atmosphere it loses its water. This process changes tyuyamunite into a different mineral known as metatyuyamunite[6] Ca(UO2)2(VO4)2·3-5H2O[7]

References

  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. Handbook of Mineralogy
  3. Tyuyamunite at Mindat
  4. Tyuyamunite data on Webmineral
  5. Tyuyamunite at Amethyst Galleries' Mineral Gallery
  6. Lynch, Dan R. and Bob Lynch, "Tyuyamunite," Ed. Brett Ortler, Michigan Rocks & Minerals, Adventure Publications, 2010 ISBN 978-1591932390
  7. Metatyuyamunite on Mindat
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