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Sulfides·Sulfosalts·Monoclinic

Pearceite

[(Ag9CuS4)][(Ag,Cu)6As2S7]

Hardness
2.5–3
Streak
Black. May have a red tinge.
Spec. Gravity
6.0–6.2
System
Monoclinic

About

Pearceite is an uncommon mineral containing silver and copper in its structure. It forms a series with Polybasite, with Pearceite being the arsenic-rich member and Polybasite being the antimony-rich member. It is often not possible to visually distinguish these two minerals from each other. Pearceite is named in honor of Dr. Richard Pearce (1837-1927), a Cornish-American chemist from Colorado. 
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Crystal Forms & Aggregates

Striking Features

Crystal habits, streak, and mode of occurrence.

Uses

Pearceite is as an ore of silver.

Noteworthy Localities

Pearceite is not a common mineral. Worldwide localities include Měděnec, Chomutov District, Bohemia, Czech Republic; the Uchucchacua Mine, Oyon Province, Lima Department, Peru; and the San Juan de Rayas Mine, Guanajuato, Mexico. In the U.S., Pearceite has come from the Mollie Gibson Mine, Aspen, Pitkin County, Colorado; and from Neihart, Cascade Co., Montana.

Common Mineral Associations

Distinguishing Similar Minerals

Polybasite - Indistinguishable without complex methods.

Photos

Crystal forms

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Pseudohexagonal
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