Formula: CuZn(CO3)(OH)2
Anhydrous carbonate containing hydroxyl
Specific gravity: 4 to 4.2
Hardness: 4½
Streak: Light blue
Colour: Blue, blue-green to green, sky-blue; colourless to light blue in transmitted light.
Solubility: Soluble in acids.

Hydrothermal environments

Rosasite is an uncommon secondary mineral found in the oxidation zone of copper-zinc deposits, typically formed by zinc-bearing solutions acting on primary copper minerals; it may be of post-mine origin (Mindat, HOM). Associated minerals include malachite, aurichalcite, hydrozincite and hemimorphite (HOM).
Rosasite is far more common in the carbonate-rich English Pennines than in carbonate-deficient deposits (JRS 18.15).

At Broken Hill, New south Wales, Australia, rosasite occurs occasionally with smithsonite and hemimorphite, and also on massive quartz-cerussite aggregates, sometimes overgrowing malachite (AJM 3.39).

At the Shangri La mine, Kimberley, Western Australia, rosasite occurs as crusts on hemimorphite, smithsonite or matrix (AJM 16.1.22).

At the Braeside lead field, Pilbara, Western Australia, rosasite is intergrown with hemimorphite and cerussite, and also occurs in association with hydrozincite (AJM 13.2.60).

At the type locality, the Rosas Mine, Narcao, Carbonia-Iglesias Province, Sardinia, Italy, rosasite occurs in the oxidised zone of a zinc-copper deposit associated with siderite, malachite, greenockite, brochantite and aurichalcite (Mindat, Dana).

At Tsumeb, Namibia, rosasite is associated with malachite, smithsonite and hydrozincite (Dana).

At Roughton Gill mine, Roughton Gill, Cumbria, England, UK, rosasite is associated with hemimorphite (JRS 11.22).

At Silver Gill, Roughton Gill, Cumbria, England, UK, rosasite is associated with aurichalcite, hemimorphite and malachite (JRS 8-2.93).

In Arizona, USA, rosasite occurs in quartz vugs associated with brochantite, cerussite, hemimorphite, malachite, and smithsonite (R&M 90.4.345).

At Cerro Gordo, Onyo county, California, USA, rosasite is associated with smithsonite and hemimorphite (Dana).

At the San Rafael mine, Nye county, Nevada, USA, rosasite is associated with hemimorphite, mimetite and cerussite, all on a matrix of spongy vein quartz (R&M 85.6.521).

At the Kelly mine, Socorro county, New Mexico, USA, rosasite is associated with aurichalcite (Dana).

At the Kabwe mine, Central Province, Zambia, rosasite has been found associated with malachite, and also as inclusions in mottramite (R&M 94.2.134)

Common impurities: Mg,Fe

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