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Chalcocite

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Formula:
Cu2S
System:
Monoclinic
Colour:
Blue black, gray, black, ...
Lustre:
Metallic
Hardness:
2½ - 3
Name:
Named chalcosine in 1832 by Fracois Sulpice Beudant from Greek, "chalkos", copper. This mineral was known by a wide variety of names previously. In 1868, James D. Dana and George J. Brush re-named this material "chalcocite"
Chalcocite-Digenite Group. Chalcocite-Yarrowite Series.

A secondary mineral in or near the oxidized zone of copper sulfide deposits. Hexagonal above 105 °C ('High-chalcocite').
Easily confused with djurleite.

Small amounts of the Cu2S phase may deposit from supersaturated volcanic gas, as shown in an experiment (Africano et al., 2002; 300-700oC deposition range for this particular experiment).

Classification of Chalcocite

Approved, 'Grandfathered' (first described prior to 1959)
2.BA.05

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
B : Metal Sulfides, M: S > 1: 1 (mainly 2: 1)
A : With Cu, Ag, Au
2.4.7.1

2 : SULFIDES
4 : AmBnXp, with (m+n):p = 2:1
3.1.1

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

Metallic
Diaphaneity (Transparency):
Opaque
Colour:
Blue black, gray, black, black gray, or steel gray
Streak:
Blackish lead gray
Hardness (Mohs):
2½ - 3
Hardness (Vickers):
VHN100=84 - 87 kg/mm2
Tenacity:
Brittle
Cleavage:
Poor/Indistinct
Indistinct on (110)
Fracture:
Conchoidal
Comment:
Somewhat sectile
Density:
5.5 - 5.8 g/cm3 (Measured)    5.8 g/cm3 (Calculated)

Crystallography of Chalcocite

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Space Group Setting:
P21/c
Cell Parameters:
a = 15.246(4) Å, b = 11.884(2) Å, c = 13.494(3) Å
β = 116.35(1)°
Ratio:
a:b:c = 1.283 : 1 : 1.135
Unit Cell Volume:
V 2,190.86 ų (Calculated from Unit Cell)
Twinning:
Common on {110} yielding pseudohexagonal stellate forms. Also on {032}, {112}.
Comment:
May be point group m and space group Pc; other monoclinic cell given: a = 11.82, b = 27.05, c = 13.43, β = 90°.

Crystallographic forms of Chalcocite

Crystal Atlas:
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Chalcocite no.48 - Goldschmidt (1913-1926)
Chalcocite - Penetration twin on {032}
Chalcocite - Multiple twin on {110}
3d models and HTML5 code kindly provided by www.smorf.nl.

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Opaque | Translucent | Transparent

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X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction Data:
d-spacingIntensity
3.276 (35)
2.7256 (35)
2.4074 (50)
2.4030 (70)
1.9746 (70)
1.8811 (70)
1.8800 (100)
Comments:
Similar to djurleite.

Optical Data of Chalcocite

Type:
Anisotropic
Anisotropism:
Weak

Chemical Properties of Chalcocite

Formula:
Cu2S
All elements listed in formula:
Common Impurities:
Fe

Relationship of Chalcocite to other Species

Series:
Forms a series with Yarrowite (see here)
Structurally related to group(s):
2.BA.05DjurleiteCu31S16
2.BA.05GeeriteCu8S5
2.BA.05RoxbyiteCu9S5
2.BA.10AniliteCu7S4
2.BA.10DigeniteCu9S5
2.BA.15BorniteCu5FeS4
2.BA.20BellidoiteCu2Se
2.BA.20BerzelianiteCu2Se
2.BA.25AthabascaiteCu5Se4
2.BA.25UmangiteCu3Se2
2.BA.30RickarditeCu7Te5
2.BA.30WeissiteCu2-xTe
2.BA.35AcanthiteAg2S
2.BA.40MckinstryiteAg5-xCu3+xS4
2.BA.40StromeyeriteAgCuS
2.BA.40dUM2003-13-S:AgAuCuAg6AuCu2S5
2.BA.45JalpaiteAg3CuS2
2.BA.45SelenojalpaiteAg3CuSe2
2.BA.50EucairiteAgCuSe
2.BA.55AguilariteAg4SeS
2.BA.55NaumanniteAg2Se
2.BA.60CervelleiteAg4TeS
2.BA.60HessiteAg2Te
2.BA.60ChenguodaiteAg9Fe3+Te2S4
2.BA.65Henryite(Cu,Ag)3+xTe2 , with x ~ 0.40
2.BA.65StütziteAg5-xTe3, x = 0.24-0.36
2.BA.70ArgyroditeAg8GeS6
2.BA.70CanfielditeAg8SnS6
2.BA.70Putzite(Cu4.7Ag3.3)GeS6
2.BA.75FischesseriteAg3AuSe2
2.BA.75Penzhinite(Ag,Cu)4Au(S,Se)4
2.BA.75PetrovskaiteAuAg(S,Se)
2.BA.75PetziteAg3AuTe2
2.BA.75UytenbogaardtiteAg3AuS2
2.BA.80Bezsmertnovite(Au,Ag)4Cu(Te,Pb)
2.BA.80BilibinskitePbCu2Au3Te2
2.BA.80Bogdanovite(Au,Te,Pb)3(Cu,Fe)
3.1.2DjurleiteCu31S16
3.1.3DigeniteCu9S5
3.1.4AniliteCu7S4
3.1.5RoxbyiteCu9S5
3.1.6SpionkopiteCu39S28
3.1.7GeeriteCu8S5
3.1.8CovelliteCuS
3.1.9BerzelianiteCu2Se
3.1.10BellidoiteCu2Se
3.1.11UmangiteCu3Se2
3.1.12YarrowiteCu9S8
3.1.13AthabascaiteCu5Se4
3.1.14KlockmanniteCuSe
3.1.15Krut'aiteCuSe2
3.1.16WeissiteCu2-xTe
3.1.17RickarditeCu7Te5
3.1.18VulcaniteCuTe
3.1.19BambollaiteCu(Se,Te)2
3.1.20LautiteCuAsS
3.1.21MgriiteCu3AsSe3
3.1.22CubaniteCuFe2S3
3.1.23BorniteCu5FeS4
3.1.24FukuchiliteCu3FeS8
3.1.25ChalcopyriteCuFeS2
3.1.26MooihoekiteCu9Fe9S16
3.1.27HaycockiteCu4Fe5S8
3.1.28IsocubaniteCuFe2S3
3.1.29IdaiteCu5FeS6
3.1.30NukundamiteCu3.4Fe0.6S4
3.1.31PutoraniteCu1.1Fe1.2S2
3.1.32Orickite2CuFeS2 · H2O
3.1.33EskeborniteCuFeSe2
3.1.34Chaméanite(Cu,Fe)4As(Se,S)4
3.1.35TalnakhiteCu9(Fe,Ni)8S16

Other Names for Chalcocite

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 Chalcocite

Reference List:
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, 834pp.: 187-190.

Zeitschrift für Kristallographie 150, 299-320.

Cook, W.R. (1972): Instability of chalcocite. Mineralogical Record 3, 15.

Pósfai, M. & Buseck, P. R. (1994): Djurleite, digenite, and chalcocite: Intergrowths and transformations. American Mineralogist, 79, 308-315.

Africano, F., Van Rompaey, G., Bernard, A., Le Guern, F. (2002): Deposition of trace elements from high temperature gases of Satsuma-Iwojima volcano. Earth Planets Space: 54: 275-286

Internet Links for Chalcocite

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

Localities for Chalcocite

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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