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Large Pearceite Crystal

The Mineral pearceite




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. 
Chemical Formula [(Ag9CuS4)][(Ag,Cu)6As2S7]
Composition Silver and copper arsenic sulfide, often with some antimony
Variable Formula [(Ag9CuS4)][(Ag,Cu)6(As,Sb)2S7]
Color Dark gray to nearly black. May have occasional internal red reflections.
Streak Black. May have a red tinge.
Hardness 2.5 - 3
Crystal System Monoclinic
3D Crystal Atlas
(Click for animated model) 
Crystal Forms
and Aggregates
As short tabular crystals, often pseudohexagonal in shape due to twinning on the prism-planes. Also platy, bladed, in rosettes, grainy, flaky, and massive. Crystals are often striated with triangular striation patterns.
Transparency Opaque
Specific Gravity 6.0 - 6.2
Luster Metallic
Cleavage 1,3
Fracture Uneven
Tenacity Brittle
In Group Sulfides; Sulfosalts
Striking Features Crystal habits, streak, and mode of occurrence.
Rock Type Sedimentary, Metamorphic
Popularity (1-4) 4
Prevalence (1-3) 3
Demand (1-3) 2


Pearceite AUCTIONS
OTHER NAMES
Arsenpolybasite



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
Polybasite, Quartz, Calcite, Barite, Acanthite, Tetrahedrite, Silver, Proustite

DISTINGUISHING SIMILAR MINERALS
Polybasite - Indistinguishable without complex methods.


pearceite PHOTOS
 
ADDITIONAL RESOURCES
 
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