Mineralpedia Details for Pearceite

Named after Dr. Richard Pearce, a Cornish-American chemist and metallurgist from Colorado, USA. Pearceite forms in hydrothermal deposits of low to medium temperatures and forms a series with polybasite. It can be found in a couple hundred localities including in the United States, Canada, Mexico, Chile, Slovakia, Germany, Spain, Italy, the Channel Islands, and Japan among other minor localities. Pearceite was originally thought to be the arsenic analogue of polybasite.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/pearceite.pdf

Formula

Cu(Ag,Cu)₆Ag₉As₂S₁₁ 

Crystal System

Trigonal 

Crystal Habit

Massive - Granular, Granular 

Cleavage

Poor, None, None 

Luster

Sub Metallic 

Color

black 

Streak

reddish black 

Class

Trigonal - Hexagonal Scalenohedral 

Fracture

Conchoidal - Irregular 

Hardness

3 

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Two large, nearly perfect crystals to 1cm. These are amazingly thick tabular to 5mm composed of multiple plates and very brilliant metallic.

9mm hexagonal platy crystal with mirror-like reflections.

Superb silvery, well-formed, hexagonal platesd to 3.5mm.