underthescopemineral:

Brochantite

Cu₄SO₄(OH)₆

Locality:

Los Azules mine, Quebrada San Miguel, Copiapó Province, Atacama Region, Chile

Field of view: 3.09 mm

Photo by 

Laurent Kbaier

Brochantite is a sulfate mineral, one of a number of cupric sulfates.

Formed in arid climates or in rapidly oxidizing copper sulfide deposits. 

Brochantite is a common corrosion product on bronze sculptures located in urban areas, where atmospheric sulfur dioxide (a common pollutant) is present. Brochantitie forms mainly in exposed areas where weathering prevents accumulation copper ions and enhancement in the acidity of water films. In sheltered areas, the main corrosion product is antlerite.