Formula: Zn2(AsO4)(OH)(H2O).2H2O
Hydrated arsenate
Crystal System: Monoclinic
Specific gravity: 3.197 (calculated)
Hardness: 1
Streak: White
Colour: Sky blue to very pale blue, white, colourless
Environments
Ianbrucite is a rare arsenate that forms during the oxidation of base-metal sulphide minerals
(R&M 91.1.80).
Localities
At the type locality, the Tsumeb Mine, Oshikoto Region, Namibia, ianbrucite occurs as a
secondary mineral in the oxidised zone of a polymetallic
sulphide deposit, associated with leiteite,
köttigite,
legrandite and adamite
(HOM, Mindat).
At the Driggith mine, Caldbeck Fells, Cumbria, England, ianbrucite occurs as a late-stage
supergene mineral in low-temperature
lead - zinc -
copper
veins. It has been found scattered on quartz -
dolomite matrix associated
with sphalerite,
chalcopyrite,
köttigite and adamite.
Arsenopyrite is abundant there, and its oxidation in veins that also
contain primary
lead, zinc and
copper
sulphides has produced a range of supergene
arsenates
(M&M 34.8-10, Wiki).
At Potts Gill mine, Caldbeck Fells, Cumbria, England, ianbrucite has been found as crusts on fractures in
blocks containing
marcasite, galena,
sphalerite and
arsenopyrite on
dolomite matrix from low-temperature
lead - zinc -
copper veins
(M&M 34.10-11, Wiki).
Ianbruceite from Potts Gill - Image
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