Daubréeite

Not to be confused with the sulfide mineral Daubréelite.

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]

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]

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]