| Tyuyamunite | |
| Category: | Vanadate mineral |
| Formula: | Ca(UO2)2V2O8·(5–8)H2O |
| Imasymbol: | Tyu[1] |
| Strunz: | 4.HB.25 |
| Dana: | 40.2a.26.1 |
| System: | Orthorhombic |
| Class: | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Symmetry: | Pnna |
| Unit Cell: | a = 10.63 Å, b = 28.36 Å c = 20.4 Å; Z = 4 |
| Colour: | Canary yellow, lemon-yellow; greenish yellow (upon exposure to sunlight) |
| Habit: | Platy crystals often in radiating sprays, coatings, massive |
| Cleavage: | Perfect on, micaceous; distinct on & |
| Mohs: | – 2 |
| Lustre: | Adamantine, waxy, pearly on, dull |
| Streak: | Yellow |
| Diaphaneity: | Translucent to opaque |
| Gravity: | 3.57 – 4.35 |
| Opticalprop: | Biaxial (−) |
| Refractive: | 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: | 30° to 45° |
| Dispersion: | none |
| Other: | Radioactive |
| References: | [2] [3] [4] [5] |
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 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]