Aurichalcite

Aurichalcite from the Ojuela Mine, Mapimi, Durango, Mexico, measuring 52 × 44 × 26 mm and weighing 48 grams. A good small piece of one of the signature secondary minerals from the world's single most productive locality for the species.

Aurichalcite is a hydrated zinc copper carbonate, (Zn,Cu)5(CO3)2(OH)6, monoclinic, and it classically forms as fine, acicular sprays and crusts in pale blue-green shades, developing in the oxidised zone of a mixed zinc-copper deposit where weathering of the primary sulfide ore releases both metals into solution together. The Ojuela Mine's immense, deeply weathered skarn orebody, worked since colonial times, has produced Aurichalcite in a quantity and quality few other localities anywhere can match, alongside its far longer list of other secondary species.

A good Ojuela Aurichalcite is, for many collectors, the reference standard against which the species from any other locality is judged. This piece is from the David Vince Collection.