Proustite
Silver Arsenic Sulfide, Ag3AsS3
Crystal System: Trigonal
Hardness: 2.0-2.5
Density: 5.57

Proustite occurs as a late-stage mineral found in hydrothermal veins of low temperature origin with other silver sulfosalts. It is associated with pyrargyrite in silver veins. Proustite and pyrargyrite are known as ruby silver ores.

Proustite crystals are usually massive and shiny dark red. They occur less commonly as striated rhombohedral or scalenohedral crystals which are often distorted and twinned. Transparent crystals are affected by exposure to light which may cause them to darken and become opaque.

Stuart provides the following remarks:

"This is a very important single double terminated floater Proustite crystal from Chile. It is from the collection of the 19th century mineralogist George J. Brush. He was the Curator of the mineral collection at Yale University during the 1870's. This crystal is very fine because it retains its original gemmy "ruby" red transparency even though it has been out of the ground for over 100 years. Don't worry, I keep it in the dark at all times!"

Rocks from Stuart Wilensky's Collection

Index of Specimen Images

Table of Contents

bkeller@rockhounds.com 7/29/95