Polybasite: The mineral polybasite information and pictures

About

Polybasite is an uncommon mineral containing silver and copper in its structure. It is almost always found in known silver deposits, often in association with Stephanite. Polybasite forms a series with Pearceite, with Polybasite being the antimony-rich member, and Pearceite being the arsenic-rich member. It is often not possible to visually distinguish these two minerals from each other. Polybasite is named from the Greek words, poly, "many" and basis, "base" referring to its composition of several metallic and submetallic elements.

Crystal Forms & Aggregates

Most often pseudohexagonal in shape, due to twinning on the prism-planes. Crystals are usually tabular, platy, bladed, or in rosette habit. Often striated with triangular striation patterns. Also grainy, flaky, and massive.

Striking Features

Crystal habits, streak, and mode of occurrence.

Environment

Low temperature epithermal veins in silver ore deposits.

Varieties

✓ common · ✗ uncommon

Polybasite-Tac— A polytype of Polybasite, with the same chemical formula but different crystal structure. Polybasite-Tac is therefore classified as an individual mineral species. Polybasite-Tac was previously known as Antimonpearceite, and was renamed by the IMA in 2006.

Uses

An ore of silver and rare collector's mineral.

Noteworthy Localities

Polybasite is not a common mineral. In Europe, well-formed micro hexagonal crystals come from the Clara Mine, Rankach valley, Oberwolfach, Baden-Württemberg, Germany. Small flaky crystals have come from the Příbram area, Bohemia, Czech Republic. In Peru, Polybasite occurs with Pyrargyrite at the Uchucchacua Mine, Oyon Province, Lima Department.
Mexico contains several notable localities for this mineral. Large, well-formed crystals of Polybasite have come from the San Juan de Rayas Mine, Guanajuato; and large single crystals and groups from the Chispas Mine, Arizpe, Sonora. Crystal clusters with Calcite have come from the Proano Mine, Fresnillo, Zacatecas.
Polybasite is very rare in U.S.: Crudely formed crystal clusters have come from the Eagle Mine, Gilman, Eagle Co., Colorado. In Canada, exceptional, well-formed, iridescent crystals came from a small find Husky Mine, Elsa, Galena Hill, Mayo Mining District, Yukon Territory. Small crystals and flakes come from Cobalt, Timiskaming District, Ontario.

Common Mineral Associations

Quartz, Galena, Chalcopyrite, Calcite, Stephanite, Silver, Pyrargyrite

Distinguishing Similar Minerals

Hematite - Has a greater hardness, redder streak, and is slightly attracted to magnets.Stephanite - Difficult to distinguish, although crystals are usually thicker.Pearcite - Indistinguishable without complex methods.