Proustite from Chile, Atacama, Chañarcillo Mining District

Proustite

Chañarcillo, Copiapó Province, Atacama Region, Chile

7.7 x 5.0 cm (152 g)

Ex. Harvard Mineralogical Museum

This is a bright, lively Chañarcillo proustite, with matrix completely carpeted in sharp, lustrous crystals. The crystals grow in radiating sprays and rosettes that rise into two raised clusters at the top of the piece, with a shallow, crystal-lined hollow between them. Many of the crystals are sharp, pointed scalenohedra with glassy faces, and a few larger bladed crystals with striated, mirror-like faces are tucked into the upper sprays. What sets this piece apart is the color. Most of the crystals are still a vivid, saturated cherry red with a brilliant adamantine luster, and they show little of the gray darkening that dulls so many older proustites. In good light the whole surface sparkles. A few touches of dark sulfide and pale gangue show through between the sprays and add some contrast without distracting from the proustite. The specimen has an attractive upright, sculptural shape and makes a strong display piece from the front, and the crystal coverage continues around the sides.

Chañarcillo was one of the great silver districts of the 19th century and remains the classic locality for proustite. Its ruby silver specimens set the standard for the species, and because the mines have long been inactive, nearly all good examples available today come from older collections. This specimen comes from one of the most distinguished of them: it was once part of the collection of the Harvard Mineralogical Museum, among the oldest and most important mineral collections in North America. Fully crystallized matrix pieces that still have this much bright, unaltered red color are increasingly hard to find, and the Harvard provenance makes this an especially desirable example from the most famous proustite locality.