Formula: Cu2Cl(OH)3
Hydroxylhalide, atacamite group, paramorph of atacamite and clinoatacamite
Specific gravity: 3.6
Hardness: soft
Streak: Light green
Colour: Bluish green to green, pale bluish green in transmitted light

Hydrothermal environments

Botallackite is a secondary copper mineral in copper-bearing deposits, in areas with high chlorine concentrations, or weathered while exposed to seawater; it is a reaction product of slag immersed in seawater and a weathering product of sulphides in subsea black smoker deposits (Webmin, HOM).


At the type locality, Wheal Cock, Botallack Mine, Botallack, St Just, Cornwall, England, UK, botallackite occurs as crusts of minute platy interlaced crystals in a copper deposit, in areas weathered while exposed to sea water. Associated minerals include atacamite and paratacamite (Mindat, HOM).

At Dalbeattie, Dumfries and Galloway, Scotland, UK, botallackite is associated with gypsum, brochantite and connellite (HOM).

At the Gallagher Vanadium & Rare Minerals Corporation Mine, Cochise county, Arizona, USA, botallackite occurs as sparse, pale green needles to 0.2 mm, associated with anglesite, brochantite and bromine-bearing chlorargyrite on the mine dump (R&M 90.4.342).

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