Localities
At Bou Azzer, Morocco cornubite has been found in quartz cavities together with scorodite (MinRec 38.5.
At the type locality, Wheal Carpenter, Cornwall, England cornubite occurs in copper-tin-silver bearing hydrothermal veins, associated with cornwallite, chalcophyllite, olivenite, liroconite, chenevixite, clinoclase, pseudomalachite, bayldonite, parnauite, tyrolite, azurite, malachite, cuprite, chrysocolla and quartz (HOM).
Cornubite from Wheal Carpenter - Image
At the San Rafael mine, Nye county, Nevada, USA, cornubite has been found with olivenite and strashimirite (R&M 85.6.517).
At the Tintic Mining District, Juab County, Utah, USA,cornubite is quite rare, but it has been found both at the Centennial Eureka mine and at the Mammoth mines. At the Centennial Eureka mine, it occurs as well-formed crystals and as rosettes of pale green platelike crystals, up to 0.5 mm in size, on quartz associated with malachite. It has also been found associated with enargite, olivenite and clinoclase at the Mammoth mine (MinRec 55.2.196).
Cornubite from the Tintic Mining District - Image
Stability
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).
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).
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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