Daubréeite

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]

Not to be confused with the sulfide mineral Daubréelite.
Daubréeite
General
CategoryOxide mineral
Formula
(repeating unit)		BiO(OH,Cl)
IMA symbolDau[1]
Strunz classification3.DC.25
Crystal systemTetragonal
Crystal classDitetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)
Space groupP4/nmm
Unit cella = 3.85, c = 7.4 [Å]; Z = 2
Identification
ColorCreamy-white, grayish, yellowish-brown
Crystal habitCompact massive, columnar
Cleavage[{001}, perfect
TenacityVery plastic, sectile
Mohs scale hardness2-2.5
LusterGreasy, silky
DiaphaneityTransparent to translucent
Specific gravity6-6.5
Optical propertiesUniaxial (-)
Refractive indexnω = 2.150 nε = 1.910
Birefringenceδ = 0.240
References[2][3][4]

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]

References
  1. 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.
  2. Daubréeite on Mindat
  3. Daubréeite on Webmineral
  4. Daubréeite in the Handbook of Mineralogy
  5. Domeyko (1876). "Daubréite(oxychlorure de bismuth), espèce minérale nouvelle". Comptes Rendus de l'Académie des Sciences de Paris. 82: 922–923.


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