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Formula: Ca2Co(AsO4)2.2H2O
Hydrated normal arsenate,
fairfieldite group, triclinic
paramorph of monoclinic roselite,
cobalt-bearing mineral, forms a series with
talmessite
Specific gravity: 3.71
Hardness: 3½ to 4
Streak: Pale red
Colour: Dark rose red, dark pink
Common impurities: Mg
Environments
Roselite-beta is a rare secondary mineral in
cobalt-bearing hydrothermal mineral deposits
(HOM).
Localities
At Dome Rock Copper Mine, Boolcoomatta Reserve, Olary Province, South Australia, roselite-beta is
associated with erythrite,
arthurite, conichalcite,
chenevixite, scorodite,
cobaltaustinite and
heterogenite
(HOM).
At the type locality, Schneeberg, Erzgebirgskreis, Saxony, Germany, roselite-beta occurs as granular masses
associated with pale pink cobalt-bearing
calcite and a few grains of dark rose-coloured
roselite, in vein material consisting principally of
quartz and pyrite. All of the minerals
appear to be primary hydrothermal deposits
(AM 40.832-833)
At the Bou Azzer mining district, Drâa-Tafilalet Region, Morocco, roselite-beta and
talmessite are almost indistinguishable from each other. They are rare
world-wide but widespread here, occurring rarely as free-standing crystals to 1 cm in size, and more commonly as rounded
clusters, subparallel aggregates and coral-like spherules. Crystals of roselite-beta with
talmessite cores have been found resting on a
dolomite matrix associated with
wendwilsonite, and epitactic intergrowths of roselite-beta and
roselite have been found in cavities in
dolomite associated with
cobaltlotharmeyerite and
cobaltaustinite
(Min Rec 38-5.393).
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