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Sylvanite

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Formula:
(Au,Ag)2Te4
Au:Ag ratio usually is close to 1:1
System:
Monoclinic
Colour:
Grey, white, pale yellow ...
Lustre:
Metallic
Hardness:
1½ - 2
Name:
Named in 1835 by Louis Albert Necker de Sausaure for the Transylvania region of Romania, where it was first found, and Sylvanium, one of the names proposed for the newly discovered element tellurium, which it contains.
Compare krennerite.

Classification of Sylvanite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
2.EA.05

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
E : Metal Sulfides, M: S <= 1:2
A : M:S = 1:2 - With Cu, Ag, Au
2.12.13.3

2 : SULFIDES
12 : AmBnXp, with (m+n):p = 1:2
3.3.9

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

Year of Discovery:
1835

Occurrences of Sylvanite

Geological Setting:
Low temperature hydrothermal veins. Late forming mineral in medium to high temperature hydrothermal veins.

Physical Properties of Sylvanite

Metallic
Diaphaneity (Transparency):
Opaque
Colour:
Grey, white, pale yellow silver-white
Streak:
Silver-white
Hardness (Mohs):
1½ - 2
Hardness (Vickers):
VHN100=154 - 172 kg/mm2
Tenacity:
Brittle
Cleavage:
Perfect
on {010}
Fracture:
Irregular/Uneven
Density:
8.16 g/cm3 (Measured)    8.161 g/cm3 (Calculated)

Crystallography of Sylvanite

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P2/b
Cell Parameters:
a = 8.95(1) Å, b = 4.478(5) Å, c = 14.62(2) Å
β = 145.35(5)°
Ratio:
a:b:c = 1.999 : 1 : 3.265
Unit Cell Volume:
V 333.14 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Short prismatic, thick tabular, skeletal, bladed, columnar, granular.
Twinning:
Common on {100}

Crystallographic forms of Sylvanite

Crystal Atlas:
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Sylvanite - {100}, {010}, {101}, highly modified
Sylvanite - {100}, {010}, {-101}, {-103}, highly modified
3d models and HTML5 code kindly provided by www.smorf.nl.

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Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

View
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.

Optical Data of Sylvanite

Type:
Anisotropic
Anisotropism:
Very strong
Colour in reflected light:
Creamy white
Pleochroism:
Strong
Comments:
Cream white to leather brown.

Chemical Properties of Sylvanite

Formula:
(Au,Ag)2Te4

Au:Ag ratio usually is close to 1:1
Essential elements:
All elements listed in formula:
Common Impurities:
Sb,Pb,Cu,Ni

Relationship of Sylvanite to other Species

2.EA.10CalaveriteAuTe2
2.EA.15KostoviteCuAuTe4
2.EA.15KrenneriteAu3AgTe8
2.EA.20BerndtiteSnS2
2.EA.20KitkaiteNiTeSe
2.EA.20MeloniteNiTe2
2.EA.20Merenskyite(Pd,Pt)(Te,Bi)2
2.EA.20Moncheite(Pt,Pd)(Te,Bi)2
2.EA.20ShuangfengiteIrTe2
2.EA.20SudovikovitePtSe2
2.EA.25VerbeekitePdSe2
2.EA.30DrysdalliteMo(Se,S)2
2.EA.30JordisiteMoS2
2.EA.30MolybdeniteMoS2
2.EA.30TungsteniteWS2
3.3.1CalaveriteAuTe2
3.3.2KrenneriteAu3AgTe8
3.3.3KostoviteCuAuTe4
3.3.4UytenbogaardtiteAg3AuS2
3.3.5FischesseriteAg3AuSe2
3.3.6PetrovskaiteAuAg(S,Se)
3.3.7PetziteAg3AuTe2
3.3.8MuthmanniteAuAgTe2
3.3.10Penzhinite(Ag,Cu)4Au(S,Se)4
3.3.11Bezsmertnovite(Au,Ag)4Cu(Te,Pb)
3.3.12BilibinskitePbCu2Au3Te2
3.3.13Bogdanovite(Au,Te,Pb)3(Cu,Fe)
3.3.14Montbrayite(Au,Sb)2Te3

Other Names for Sylvanite

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 Sylvanite

Reference List:
von Reichenstein (1785): Phys. Arb. Wien: 3: 48.

von Born (1790): 2: 467.

Klaproth, M.H. (1802): Chemische Untersuchung der siebenbürgischen Golderze, B. Schrifterz, Beiträge zur chemischen Kenntniss der Mineralkörper, Dritter Band, Rottmann Berlin, 16-19

Necker (1835). Sylvanit. [?]

Palache, C. (1900): American Journal of Science: 10: 419.

Spencer (1903): Mineralogical Magazine: 13: 271.

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: 338-341.

American Mineralogist (1949): 34: 342.

Tschermaks Mineralogische und Petrographische Mitteilungen (1984): 33: 203-212.

Internet Links for Sylvanite

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

Localities for Sylvanite

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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