Daubréeite | |
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General | |
Category | Oxide mineral |
Formula (repeating unit) | BiO(OH,Cl) |
IMA symbol | Dau [1] |
Strunz classification | 3.DC.25 |
Crystal system | Tetragonal |
Crystal class | Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) |
Space group | P4/nmm |
Unit cell | a = 3.85, c = 7.4 [Å]; Z = 2 |
Identification | |
Color | Creamy-white, grayish, yellowish-brown |
Crystal habit | Compact massive, columnar |
Cleavage | [{001}, perfect |
Tenacity | Very plastic, sectile |
Mohs scale hardness | 2-2.5 |
Luster | Greasy, silky |
Diaphaneity | Transparent to translucent |
Specific gravity | 6-6.5 |
Optical properties | Uniaxial (-) |
Refractive index | nω = 2.150 nε = 1.910 |
Birefringence | δ = 0.240 |
References | [2] [3] [4] |
Daubréeite is a rare bismuth oxohalide mineral with formula BiO(OH,Cl). It is a creamy-white to yellow-brown, soft, earthy clay–like mineral which crystallizes in the tetragonal crystal system. It is a member of the matlockite group. [2]
It was first described for an occurrence in the Constanicia mine, Tazna, Bolivia, in 1876. [5] It was named for French mineralogist Gabriel Auguste Daubrée (1814–1896). [2] At the Tanza location it occurs as a secondary mineral formed by the oxidation of native bismuth or bismuthinite. It occurs with clay minerals. [4] In addition to its discovery location it has also been reported from the Tintic District in the East Tintic Mountains of Juab County, Utah; in the Josephine Creek District of Josephine County, Oregon; in the Manhattan District of Nye County, Nevada; and the Rio Marina Mine on Elba, Italy. [2]