Guilleminite
Guilleminite | |
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A cuprosklodowskite vug filled with well formed dark green vandenbrandeite crystals. These are dusted over with small yellow crystals of guilleminite. | |
General | |
Category | Oxide minerals |
Formula (repeating unit) | Ba(UO2)3(SeO3)2(OH)4·3H2O |
IMA symbol | Gul[1] |
Strunz classification | 4.JJ.10 |
Dana classification | 34.07.03.01 |
Crystal system | Orthorhombic |
Crystal class | Pyramidal (mm2) (same H-M symbol) |
Space group | P21nm |
Unit cell | 869.48 Å3 |
Identification | |
Color | Bright yellow, greenish yellow, yellow |
Cleavage | Perfect on {100}, good on {010} |
Fracture | Brittle |
Tenacity | Brittle |
Mohs scale hardness | 2 |
Luster | Waxy, greasy, dull, earthy |
Diaphaneity | Transculent |
Specific gravity | 4.88 |
Optical properties | Biaxial (−) |
Refractive index | nα = 1.720 nβ = 1.798 nγ = 1.805 |
Birefringence | 0.085 |
Pleochroism | Strong |
2V angle | Measured 35°, calculated 32° |
Dispersion | r > v strong |
Other characteristics | |
References | [2][3][4] |
Guilleminite (Ba(UO2)3(SeO3)2(OH)4·3H2O) is a uranium mineral named by R. Pierrot, J. Toussaint, and T. Verbeek in 1965 in honor of Jean Claude Guillemin (1923–1994), a chemist and mineralogist. It is a rare uranium/selenium mineral found at the Musonoi Mine in the Katanga Province of the Democratic Republic of the Congo.[3]
This secondary mineral also includes barium in its structure, in addition to selenium and uranium. It is bright yellow in colour and usually has an acicular crystal habit. It has a Mohs hardness of 2–3.[5]
Pleochroism
[edit]Guilleminite shows strong pleochroic attributes. Depending on the axis the gem is seen, guilleminite on the X axis can be seen in a bright yellow color, on the Y axis can be seen yellow, and on the Z axis is seen as a colorless gem.
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. S2CID 235729616.
- ^ Mineralienatlas
- ^ a b Guilleminite: Guilleminite mineral information and data on Mindat.org
- ^ Webmineral data
- ^ Pierrot R, Toussaint J, Verbeek T. Bull. Soc. Franc. Mineral. Crist. 1965; 88: 132.