Chalcanthite

Chalcanthite crystallises in stubby prismatic and thick tabular forms. Its range of colours includes various shades of blue.

It is a product of the oxidation of copper sulphides, which occurs through the percolation of meteoric water and the rise of pressurised hydrothermal fluids. Soluble in water, it has an unpleasant taste (it is even poisonous if ingested), in air it dehydrates and alters on the surface.