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.[5] It was named by Konstantin Avtonomovich Nenadkevich, in 1912, after its type locality, Tyuya-Muyun, Fergana Valley, Kyrgyzstan.[2]
| Tyuyamunite | |
|---|---|
 | |
| General | |
| Category | Vanadate mineral |
| Formula (repeating unit) | Ca(UO2)2V2O8·(5-8)H2O |
| Strunz classification | 4.HB.25 |
| Dana classification | 40.2a.26.1 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pnna |
| Unit cell | a = 10.63 Å, b = 28.36 Å c = 20.4 Å; Z = 4 |
| Identification | |
| Colour | Canary yellow, lemon-yellow; greenish yellow (upon exposure to sunlight) |
| Crystal habit | Platy crystals often in radiating sprays, coatings, massive |
| Cleavage | Perfect on {001}, micaceous; distinct on {100} & {010} |
| Mohs scale hardness | 1 1⁄2 - 2 |
| Lustre | Adamantine, waxy, pearly on {101}, dull |
| Streak | Yellow |
| Diaphaneity | Translucent to opaque |
| Specific gravity | 3.57 - 4.35 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.675 nβ = 1.860 - 1.870 nγ = 1.885 - 1.895 |
| Birefringence | 0.210 - 0.220 |
| Pleochroism | weak: X = nearly colourless, Y = pale canary yellow, Z = canary yellow |
| 2V angle | 30° to 45° |
| Dispersion | none |
| Other characteristics |  Radioactive |
| References | [1][2][3][4] |
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[5] Ca(UO2)2(VO4)2·3-5H2O[6]
References
- Handbook of Mineralogy
- Tyuyamunite at Mindat
- Tyuyamunite data on Webmineral
- Tyuyamunite at Amethyst Galleries' Mineral Gallery
- Lynch, Dan R. and Bob Lynch, "Tyuyamunite," Ed. Brett Ortler, Michigan Rocks & Minerals, Adventure Publications, 2010 ISBN 978-1591932390
- Metatyuyamunite on Mindat
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