Clinoclase

clinoclase

olivenite

conichalcite

liriconite

Images

Formula: Cu3(AsO4)(OH)3
Anhydrous arsenate containing hydroxyl
Specific gravity: 4.38
Hardness: 2½ to 3
Streak: Bluish green
Colour: Dark greenish black to greenish blue
Common impurities: P
Environments:

Hydrothermal environments

Clinoclase is a rare secondary mineral in the oxidized zone of some arsenic-rich hydrothermal base-metal deposits. At the type locality, Wheal Gorland, Cornwall, England, clinoclase is associated with olivenite, liroconite and cornwallite (Mindat).

Localities

At the Clara Mine, Near Wolfach in the Black Forest, Germany, clinoclase is associated with olivenite, conichalcite, malachite and azurite, all on a baryte-rich matrix (R&M90.1.42).

The Activity-pH diagram below was calculated at 298.2 K for the main Cu2+ and Pb2+ arsenate minerals. Boundaries are calculated for constant activities (roughly equivalent to concentrations) of Pb2+ and Cl- ions in solution, over a range of values of pH and of Cu2+ activity. Higher chloride activites make the stability fields of bayldonite and duftite vanish, with respect to the encroachment of that of mimetite (LMW p269).
stability Cu Pb.jpg

The arsenate mineral formulae are:
philipsbornite PbAl3(AsO4)(AsO3OH)(OH)6
mimetite Pb5(AsO4)3Cl
duftite PbCu(AsO4)(OH)
bayldonite Cu3PbO(AsO3OH)2(OH)2
olivenite Cu2(AsO4)(OH)
cornwallite Cu5(AsO4)2(OH)4
clinoclase Cu3(AsO4)(OH)3










The Activity-pH diagram below was calculated at 298.2 K for some carbonates and copper arsenates for constant activity (roughly equivalent to concentration) of H2AsO4- in solution, over a range of values of pH and of H2CO3 activity (MM 52.687).
stability AsO4, CO3.jpg

The mineral formulae are:
azurite: Cu3(CO3)2(OH)2
malachite: Cu2(CO3)(OH)2
olivenite: Cu2(AsO4)(OH)
cornubite: Cu5(AsO4)2(OH)4
clinoclase: Cu3(AsO4)(OH)3













The Activity-pH diagram below was calculated at 298.2 K for some arsenates and sulphates for constant activity (roughly equivalent to concentration) of H2AsO4- in solution, over a range of values of pH and of SO42- activity (MM 52.689).
stability sulphates.jpg

The mineral formulae are:
chalcanthite: Cu(SO4).5H2O
antlerite: Cu2+3(SO4)(OH)4
brochantite: Cu4(SO4)(OH)6
olivenite: Cu2(AsO4)(OH)
cornubite: Cu5(AsO4)2(OH)4
clinoclase: Cu3(AsO4)(OH)3













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