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

Hydrothermal environments

Roselite-beta is a rare secondary mineral in cobalt-bearing hydrothermal mineral deposits (HOM).


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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