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Pearceite

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Formula:
[(Ag,Cu)6(As,Sb)2S7][Ag9CuS4]
System:
Trigonal
Colour:
black with dark red ...
Lustre:
Hardness:
2½ - 3
Member of:
Name:
After Dr. Richard Pearce (1837-1927) chemist and metallurgist, Denver, Colorado, USA.
Pearceite Group, Pearceite-Polybasite series.

Originally pearceite was thought to be an arsenic analogue of polybasite.
"Arsenpolybasite" was, however, found to represent two different polytypes of pearceite, pearceite-T2ac and pearceite-M2a2b2c.

Pearceite forms a series with polybasite-Tac (formerly "antimonpearceite"), which is a polytype of polybasite.

The old name pearceite will be replaced by pearceite-Tac, antimonpearceite by polybasite-Tac, arsenpolybasite-221 by pearceite-T2ac, and arsenpolybasite-222 by pearceite-M2a2b2c (Bindi et al. 2007).

Classification of Pearceite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
2.GB.15

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
G : Sulfarsenites, sulfantimonites, sulfbismuthites
B : Neso-sulfarsenites, etc. with additional S
3.1.8.1

3 : SULFOSALTS
1 : ø > 4
5.2.5

5 : Sulphosalts - Sulpharsenites and Sulphobismuthites (those containing Sn, Ge,or V are in Section 6)
2 : Sulpharsenites etc. of Ag
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Type Occurrence of Pearceite

Year of Discovery:
1896

Physical Properties of Pearceite

Colour:
black with dark red internal reflections
Streak:
black
Hardness (Mohs):
2½ - 3

Crystallography of Pearceite

Polytype:
Formula:
Crystal System:
Class (H-M)
Space Group:
Space Group Setting:
Cell Parameters:
Ratio:
Unit Cell Volume (calc):
Z:
Pearceite-M2a2b2cPearceite-T2acPearceite-Tac
   
 Monoclinic  
   
   



   
   
   

Crystallographic forms of Pearceite

Crystal Atlas:
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Pearceite - Tabular {001}
3d models and HTML5 code kindly provided by www.smorf.nl.

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Optical Data of Pearceite

Type:
Biaxial
RI values:
nα = 2.700
Max Birefringence:
δ = 2.700
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
relatively strong

Chemical Properties of Pearceite

Formula:
[(Ag,Cu)6(As,Sb)2S7][Ag9CuS4]
Essential elements:
All elements listed in formula:
Common Impurities:
Zn,Fe,Sb

Relationship of Pearceite to other Species

Series:
Forms a series with Polybasite (see here)
Member of:
Other Members of Group:
Cupropearceite[Cu6As2S7][Ag9CuS4]
Cupropolybasite[Cu6Sb2S7][Ag9CuS4]
Polybasite[(Ag,Cu)6(Sb,As)2S7][Ag9CuS4]
Selenopolybasite[(Ag,Cu)6(Sb,As)2(S,Se)7][Ag9Cu(S,Se)2Se2]
2.GB.05ArgentotennantiteAg6[Cu4(Fe,Zn)2]As4S13
2.GB.05FreibergiteAg6[Cu4Fe2]Sb4S13-x
2.GB.05GirauditeCu6[Cu4(Fe,Zn)2]As4Se13
2.GB.05GoldfielditeCu10Te4S13
2.GB.05HakiteCu6[Cu4Hg2]Sb4Se13
2.GB.05TennantiteCu6[Cu4(Fe,Zn)2]As4S13
2.GB.05TetrahedriteCu6[Cu4(Fe,Zn)2]Sb4S13
2.GB.10SelenostephaniteAg5Sb(Se,S)4
2.GB.10StephaniteAg5SbS4
2.GB.15Polybasite[(Ag,Cu)6(Sb,As)2S7][Ag9CuS4]
2.GB.15UM2003-14-S:AgBiFeTeAg16FeBiTe3S8
2.GB.15Selenopolybasite[(Ag,Cu)6(Sb,As)2(S,Se)7][Ag9Cu(S,Se)2Se2]
2.GB.15Cupropearceite[Cu6As2S7][Ag9CuS4]
2.GB.15Cupropolybasite[Cu6Sb2S7][Ag9CuS4]
2.GB.15UM1979-17-S:BiCuFeCu18Fe4BiS16
2.GB.20Galkhaite(Cs,Tl)(Hg,Cu,Zn)6(As,Sb)4S12
5.2.1SmithiteAgAsS2
5.2.2TrechmanniteAgAsS2
5.2.3ProustiteAg3AsS3
5.2.4XanthoconiteAg3AsS3
5.2.6Pearceite-T2ac
5.2.7ArgentotennantiteAg6[Cu4(Fe,Zn)2]As4S13
5.2.8MiargyriteAgSbS2
5.2.9PyrargyriteAg3SbS3
5.2.10PyrostilpniteAg3SbS3
5.2.11StephaniteAg5SbS4
5.2.12Polybasite[(Ag,Cu)6(Sb,As)2S7][Ag9CuS4]
5.2.13BillingsleyiteAg7AsS6
5.2.14Polybasite-Tac
5.2.15FreibergiteAg6[Cu4Fe2]Sb4S13-x
5.2.16AramayoiteAg(Sb,Bi)S2
5.2.17MatilditeAgBiS2
5.2.18SchapbachiteAg0.4Pb0.2Bi0.4S
5.2.19Pavonite(Ag,Cu)(Bi,Pb)3S5
5.2.20ArcubisiteAg6CuBiS4
5.2.21BohdanowicziteAgBiSe2
5.2.22SelenostephaniteAg5Sb(Se,S)4
5.2.23BenleonarditeAg8(Sb,As)Te2S3
5.2.24VolynskiteAgBiTe2

Other Names for Pearceite

Name in Other Languages:

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Pearceite

Reference List:
Rose (1833), Ann. Phys.: 28: 158.

Rammelsberg (1875): 123.

Pearce and Penfield (1892), American Journal of Science: 44: 17.

Penfield (1896), American Journal of Science: 2: 17.

Gaudin and McGlashan (1938): 33: 153.

Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 353-355.

Rep. Tohoku University (1983): 15: 3.

Harlov, D.E. (1999): Thermochemistry of Ag-Cu exchange equilibria between proustite, sinnerite, and pearceite; constraints on Ag-Cu and As-Sb mixing in pyrargyrite-proustite. European Journal of Mineralogy, 11, 709-719.

Bindi, L., M. Evain and S. Menchetti (2006): Temperature dependence of the silver distribution in the crystal structure of natural pearceite, (Ag,Cu)16(As,Sb)2S11. Acta Crystallographica B62, 212-219.

Luca Bindi, Michel Evain, Paul G. Spry, and Silvio Menchetti (2007): The pearceite-polybasite group of minerals: Crystal chemistry and new nomenclature rules. American Mineralogist, 92, 918-925.

Welberry, T. R. & Pasciak, M. (2011): Monte Carlo and molecular dynamics simulation of disorder in the Ag+ fast ion conductors pearceite and polybasite. Metallurgical and Materials Transactions A42, 6-13.

Internet Links for Pearceite

Specimens:
The following Pearceite specimens are currently listed for sale on minfind.com.

Localities for Pearceite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
Mineral and/or Locality  
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