Roselite

roselite

talmessite

erythrite

wendwilsonite

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Formula: Ca2Co(AsO4)2.2H2O
Hydrated normal arsenate, roselite group, forms a solid solution with wendwilsonite, cobalt-bearing mineral
Roselite-beta is the triclinic paramorph of roselite, which is monoclinic
Specific gravity: 3.46 to 3.74
Hardness: 3½
Streak: White to pale pink
Colour: Rose-red, pink; rose coloured in transmitted light
Solubility: Readily soluble in acids (Mindat)
Environments:

Hydrothermal environments

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

Localities

At the type locality, Rappold Mine, Saxony, Germany, roselite occurs in a quartz vein, associated with chalcedony (Mindat).

Bou Azzer, Morocco, is the finest locality in the world for roselite group minerals. Here roselite is associated with talmessite and erythrite (HOM, Dana). The general sequence of crystallisation is: tabular erythrite and roselite then wendwilsonite and roselite-beta then talmessite then acicular erythrite. Associated with the series are hematite, calcite, cobaltaustinite, cobaltlotharmeyerite and rarely spherocobaltite. Roselite-wendwilsonite is commonly associated with roselite-beta or with cobalt-rich talmessite. Both minerals occur primarily as drusy crusts in cavities; free standing crystals on dolomite or quartz are rarer (Minrec 38.5.389-393).

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