Polybasite Composition, Crystallization and Structure

Composition. Sulphantimonite of silver, Ag9SbS6 or 9Ag2S.-Sb2S3 = Sulfur 15, antimony 9.4, silver 75.6. Copper replaces a part of the silver and aersenic replaces the antimony.

Crystallization. Monoclinic. Crystals are pseusorhobohedral in symmetry, occurring in hexagonal prism, often thin tabular. Basal planes show triangular markings.

Structure. In crystals. Granular.

Physical Properties. H. = 2-3. G. = 6-6.2. Metallic luster. Color steel-gray to iron-black. Streak black.

Tests. Fusible  at 1. B. B. on charcoal gives dense white coating of antimony trioxide with odor of sulfur dioxide. After decomposition by nitric acid, the filtrate with hydrochloric acid gives white precipitate of silver chloride. To be distinguished from other similar species chiefly by its crystals.

Occurrence. A comparatively rare silver mineral, associated with other sulphantimonides of silver mines of Mexico, Chile, Saxony and bohemia. Found in the United States at the Comstock Lode, Nevada; near Ouray, Colorado; from Idaho, etc

Name. Name is in allusion to the many bases contained in the mineral.

Use. An ore of silver.