Cleavage is distinct in two directions, both perpendicular to the enlarged faces of the tabular crystals, intersecting at about 70°.

Cornubite is fairly soft, with hardness 4, the same as fluorite, and specific gravity 4.64, which is similar to another copper arsenate, clinoclase, at 4.38, but much denser than quartz, at 2.66.

Cornubite is a secondary mineral found in the oxidised zone of copper deposits.

In Cornwall it is found in drusy quartz associated with malachite, Cu2(CO3)(OH)2, olivenite, Cu2(AsO4)(OH), cuprite, Cu2O, cornwallite, Cu2+5(AsO4)2(OH)2, and liroconite, Cu2+2Al(AsO4)(OH)4·4H2O.

[3] Some of the world's best specimens come from the Majuba Hill Mine in the Antelope District, Nevada, US.