| Daubréeite | |
|---|---|
| General | |
| Category | Oxide mineral |
| Formula | 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]
