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Arsenopyrite

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Formula:
FeAsS
System:
Monoclinic
Colour:
Silver-white to ...
Lustre:
Metallic
Hardness:
5½ - 6
Name:
Named in 1847 by Ernst Friedrich Glocker for its composition, a contraction of the antiquated term "arsenical pyrite." Arsenopyrite was known much before 1847 and arsenopyrite, as a name, may be taken as a simple translation of "arsenkies".
Arsenopyrite Group.

For possible Ni analogue see Unnamed (Ni,Fe,Co)AsS; see also Unnamed (Ni Arsenide Sulphide). Arsenopyrite is closely related to Alloclasite, but is not an exact analogue, because of different As-S and S-As ordering.

Arsenopyrite may contain up to about 9 wt.% Co; with higher Co contents, Glaucodot will appear as a separate phase (Gammon, 1966).

Classification of Arsenopyrite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
2.EB.20

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
E : Metal Sulfides, M: S <= 1:2
B : M:S = 1:2, with Fe, Co, Ni, PGE, etc.
Dana 7th ed.:
2.12.4.1
2.12.4.1

2 : SULFIDES
12 : AmBnXp, with (m+n):p = 1:2
3.9.12

3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
9 : Sulphides etc. of Fe
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Occurrences of Arsenopyrite

Geological Setting:
High temperature gold-quartz or tin hydrothermal veins, pegmatites, contact metamorphic rocks, gneisses, schists.

Physical Properties of Arsenopyrite

Metallic
Diaphaneity (Transparency):
Opaque
Colour:
Silver-white to steel-grey
Streak:
Grey-black
Hardness (Mohs):
5½ - 6
Hardness (Vickers):
VHN100=1081 kg/mm2
Comment:
VHN on (001) section
Tenacity:
Brittle
Cleavage:
Distinct/Good
Distinct on {001}; {010} in traces
Fracture:
Irregular/Uneven
Density:
6.07(15) g/cm3 (Measured)    6.18 g/cm3 (Calculated)

Crystallography of Arsenopyrite

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Space Group Setting:
P21/c
Cell Parameters:
a = 5.744Å, b = 5.675Å, c = 5.785Å
β = 112.3°
Ratio:
a:b:c = 1.012 : 1 : 1.019
Unit Cell Volume:
V 174.47 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Flat tabular to blocky (sometimes pseudo-octahedral) to prismatic.
Twinning:
Common on {100} and {001}. Contact or penetration on {101}, on {012} trillings or cruciform.
Comment:
Pseudo-orthorhombic, face-centred cell: ~5.7, ~6.4, ~9.6 A.

Crystallographic forms of Arsenopyrite

Crystal Atlas:
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Click on an icon to view
Arsenopyrite no.5 - Goldschmidt (1913-1926)
Arsenopyrite no.12 - Goldschmidt (1913-1926)
Arsenopyrite no.14 - Goldschmidt (1913-1926)
Arsenopyrite no.62 - Goldschmidt (1913-1926)
Arsenopyrite no.64 - Goldschmidt (1913-1926)
Arsenopyrite no.113 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

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Along a-axis | Along b-axis | Along c-axis | Start rotation | Stop rotation
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction Data:
d-spacingIntensity
2.677 (100)
2.662 (100)
2.440 (90)
2.418 (95)
2.412 (95)
1.824 (70)
1.814 (90)

Optical Data of Arsenopyrite

Type:
Anisotropic
Anisotropism:
Strong red-violet
Reflectivity:
400nmR1=50.3%R2= 51.8%
420nmR1=50.3%R2= 51.8%
440nmR1=51.3%R2= 51.8%
460nmR1=50.6%R2= 51.8%
480nmR1=51.0%R2= 51.9%
500nmR1=51.4%R2= 51.9%
520nmR1=51.8%R2= 51.9%
540nmR1=52.2%R2= 51.9%
560nmR1=52.5%R2= 51.9%
580nmR1=53.0%R2= 51.8%
600nmR1=53.4%R2= 51.6%
620nmR1=53.6%R2= 51.5%
640nmR1=53.6%R2= 51.3%
660nmR1=53.6%R2= 51.3%
680nmR1=53.4%R2= 51.2%
700nmR1=53.2%R2= 51.0%

Reflectance graph
Graph shows reflectance levels at different wavelengths (in nm). Top of box is 100%. Peak reflectance is 53.6%.
R1 shown in black, R2 shown in red
Colour in reflected light:
White with faint yellow tint
Pleochroism:
Weak
Comments:
White or bluish tint, faint reddish yellow

Chemical Properties of Arsenopyrite

Formula:
FeAsS
Essential elements:
All elements listed in formula:
Analytical Data:
O'Brien mine, Cobalt, Canada.
Fe (34.53)
Co (0.09)
Bi (0.79)
As (44.34)
S (20.22)
Total (99.97)
Common Impurities:
Ag,Au,Co,Sn,Ni,Sb,Bi,Cu,Pb

Relationship of Arsenopyrite to other Species

Other Members of Group:
Glaucodot(Co0.50Fe0.50)AsS
GudmunditeFeSbS
Osarsite(Os,Ru)AsS
Ruarsite(Ru,Os)AsS
2.EB.05aAurostibiteAuSb2
2.EB.05bBambollaiteCu(Se,Te)2
2.EB.05aCattieriteCoS2
2.EB.05aErlichmaniteOsS2
2.EB.05aFukuchiliteCu3FeS8
2.EB.05aGeversitePtSb2
2.EB.05aHaueriteMnS2
2.EB.05aInsizwaitePt(Bi,Sb)2
2.EB.05aKrut'aiteCuSe2
2.EB.05aLauriteRuS2
2.EB.05aPenroseite(Ni,Co,Cu)Se2
2.EB.05aPyriteFeS2
2.EB.05aSperrylitePtAs2
2.EB.05aTrogtaliteCoSe2
2.EB.05aVaesiteNiS2
2.EB.05aVillamaninite(Cu,Ni,Co,Fe)S2
2.EB.05aDzharkeniteFeSe2
2.EB.05aGaotaiiteIr3Te8
2.EB.10bAlloclasiteCo1-xFexAsS
2.EB.10dCostibiteCoSbS
2.EB.10aFerroseliteFeSe2
2.EB.10aFrohbergiteFeTe2
2.EB.10cGlaucodot(Co0.50Fe0.50)AsS
2.EB.10aKulleruditeNiSe2
2.EB.10aMarcasiteFeS2
2.EB.10aMattagamiteCoTe2
2.EB.10eParacostibiteCoSbS
2.EB.10ePararammelsbergiteNiAs2
2.EB.10fOeniteCoSbAs
2.EB.15aAnduoite(Ru,Os)As2
2.EB.15aClinosaffloriteCoAs2
2.EB.15aLöllingiteFeAs2
2.EB.15aNisbiteNiSb2
2.EB.15aOmeiite(Os,Ru)As2
2.EB.15cPaxiteCuAs2
2.EB.15aRammelsbergiteNiAs2
2.EB.15aSafflorite(Co,Ni,Fe)As2
2.EB.15bSeinäjokite(Fe,Ni)(Sb,As)2
2.EB.20GudmunditeFeSbS
2.EB.20Osarsite(Os,Ru)AsS
2.EB.20Ruarsite(Ru,Os)AsS
2.EB.25CobaltiteCoAsS
2.EB.25GersdorffiteNiAsS
2.EB.25Hollingworthite(Rh,Pt,Pd)AsS
2.EB.25Irarsite(Ir,Ru,Rh,Pt)AsS
2.EB.25JolliffeiteNiAsSe
2.EB.25KrutoviteNiAs2
2.EB.25MaslovitePtBiTe
2.EB.25MicheneritePdBiTe
2.EB.25PadmaitePdBiSe
2.EB.25PlatarsitePtAsS
2.EB.25TestibiopalladitePdTe(Sb,Te)
2.EB.25TolovkiteIrSbS
2.EB.25UllmanniteNiSbS
2.EB.25Willyamite(Co,Ni)SbS
2.EB.25ChangchengiteIrBiS
2.EB.25MayingiteIrBiTe
2.EB.25Hollingsworthite
2.EB.25KalungaitePdAsSe
2.EB.25MilotaitePdSbSe
2.EB.30UrvantsevitePd(Bi,Pb)2
2.EB.35RheniiteReS2
3.9.1PyrrhotiteFe1-xS (x = 0 to 0.17)
3.9.3PyriteFeS2
3.9.4MarcasiteFeS2
3.9.5GreigiteFe2+Fe23+S4
3.9.6Mackinawite(Fe,Ni)9S8
3.9.7Smythite(Fe,Ni)3+xS4 (x=0-0.3)
3.9.8Achavalite(Fe,Cu)Se
3.9.9FerroseliteFeSe2
3.9.10FrohbergiteFeTe2
3.9.11LöllingiteFeAs2
3.9.13GudmunditeFeSbS

Other Names for Arsenopyrite

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 Arsenopyrite

Reference List:
Buerger, M. J. (1936) The symmetry and crystal structure of the minerals of the arsenopyrite group. Zeitschrift für Kristallographie, 95, 83-113.

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: 316-322.

Morimoto, N., Clark, L. A. (1961) Arsenopyrite crystal-chemical relations. American Mineralogist 46, 1448-1469.

Mineralogical Magazine (1962): 33: 263.

Brostigen, G., Kjekshus, A., Rømming, C. (1973) Compounds with the marcasite type crystal structure. VIII. Redetermination of the prototype. Acta Chemica Scandinavica, 27, 2791-2796.

Kretschmar, U., Scott, S. D. (1976) Phase relations involving arsenopyrite in the system Fe-As-S and their application. The Canadian Mineralogist, 14, 364-386.

Tossell, J. A., Vaughan, D. J., Burdett, J. K. (1981) Pyrite, marcasite, and arsenopyrite type minerals: Crystal chemical and structural principles. Physics and Chemistry of Minerals, 7, 177-184.

Fuess, H., Kratz, T., Topel-Schadt, J., Miehe, G. (1987) Crystal structure refinement and electron microscopy of arsenopyrite. Zeitschrift für Kristallographie 179, 335-346.

Fleet, M.E. and Mumin, A.H. (1997) Gold-bearing arsenian pyrite and marcasite and arsenopyrite from Carlin-trend gold deposits and laboratory synthesis. American Mineralogist 82, 182-193.

Schaufuss, A.G., Nesbitt, H.W., Scaini, M.J., Hoechst, H., Bancroft, M.G., and Szargan, R. (2000) Reactivity of surface sites on fractured arsenopyrite (FeAsS) toward oxygen. American Mineralogist 85, 1754-1766.

Tomkins A G, Frost B R, Pattison D R M (2006): Arsenopyrite melting during metamorphism of sulfide ore deposits. Canadian Mineralogist, 44, 1045-1062.

H. Yang and R.T. Downs (2008) Crystal structure of glaucodot, (Co,Fe)AsS, and its relationships to marcasite and arsenopyrite, American Mineralogist 93, 1183-1186.

Bindi L, Moëlo Y, Léone P, Suchaud M (2012): Stoichiometric arsenopyrite, FeAsS, from La Roche-Balue Quarry, Loire-Atlantique, France: Crystal structure and Mössbauer study. Canadian Mineralogist, 50, 471-479.

Kharbish, S. & András, P. (2014): Investigations of the Fe sulfosalts berthierite, garavellite, arsenopyrite and gudmundite by Raman spectroscopy. Mineralogical Magazine 78,1287-1299.

Internet Links for Arsenopyrite

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

Localities for Arsenopyrite

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.
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