Sylvanite Mineral Data

Sylvanite Mineral Data +

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General Sylvanite Information

Chemical Formula:

(Au,Ag)2Te4

Composition:

Molecular Weight = 429.89 gm

Silver 6.27 % Ag

Tellurium 59.36 % Te

Gold 34.36 % Au

______

100.00 %

Empirical Formula:

Au_0.75Ag_0.25Te₂

Environment:

Most commonly in low-temperature hydrothermal veins; also in moderate temperature and high-temperature deposits, usually among the last minerals formed.

IMA Status:

Valid Species (Pre-IMA) 1835

Locality:

Baia de Aries (Aranyosbánya, Offenbánya), Transylvania, Romania. Link to MinDat.org Location Data.

Name Origin:

Named after TranSYLVANia, for the part of Romainia where it was first found..

Synonym:

ICSD 30874

PDF 9-477

Sylvanite Image

Images:

Sylvanite

Comments: Flat-lying, metallic crystallized sylvanite on a quartz rich matrix. Caleb Simkoff Collection.
Location: Sacaramb (Nagyag), Transylvania, Romania. Scale: 7.5 x 8.5 x 4 cm.
© Dan Weinrich

Sylvanite Crystallography

Axial Ratios:

a:b:c =1.9955:1:3.2561

Cell Dimensions:

a = 8.96, b = 4.49, c = 14.62, Z = 4; beta = 145.433° V = 333.71 Den(Calc)= 8.56

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: P 2/c

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 3.05(1), 2.14(0.5), 2.25(0.3),

Forms:

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Forms: [ 1 1 1] [ 0 1 0] [ 1 1 0] [ 3 0 1] [ 1 0 0] [ 1 0 1] [ 1 0 3]

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Crystal Structure:

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Tunell G , American Mineralogist , 26 (1941) p.457-477, The atomic arrangement of sylvanite

Physical Properties of Sylvanite

Cleavage:

[010] Perfect

Color:

Yellowish silver white, White.

Density:

7.9 - 8.3, Average = 8.1

Diaphaniety:

Opaque

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Platy - Sheet forms (e.g. micas).

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Habit:

Skeletal - Crystals form crude outlines with missing faces.

Hardness:

1.5-2 - Talc-Gypsum

Luminescence:

None.

Luster:

Metallic

Magnetism:

Magnetic after heating

Streak:

steel gray

Optical Properties of Sylvanite

RL Anisotrophism:

Very strong, in grayish brown, grayish white, and yellowish and bluish tints.

RL Color:

Creamy white.

RL Pleochroism:

Strong, cream-white to leather brown.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Sylvanite in Air**
λ	R₁	R₂	∑ R₁(λ)	∑ R₂(λ)
400 nm	38.60	52.60
420 nm	41.40	54.80
440 nm	44.20	57.00
460 nm	46.40	58.50
480 nm	47.90	59.60
500 nm	49.00	60.30
520 nm	50.00	60.80
540 nm	50.60	61.10
560 nm	50.80	61.40
580 nm	51.00	61.60
600 nm	51.30	61.70
620 nm	51.60	61.90
640 nm	52.00	62.00
660 nm	52.60	62.20
680 nm	53.50	62.50
700 nm	54.80	63.10

**Calculated Relative Intensity Colors of Sylvanite in Air**
Relative Intensity	0%	30%	60%	90%	100%	120%	150%	180%	200%
R₁
R₂

Calculated Properties of Sylvanite

Electron Density:

r_electron=6.97 gm/cc
note: r_Sylvanite=8.56 gm/cc.

Fermion Index

Fermion Index = 0.04743
Boson Index = 0.95257

Photoelectric:

PE_Sylvanite= 815.38 barns/electron
U=PE_Sylvanite x r_electron=5,682.52 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Sylvanite is Not Radioactive

Sylvanite Classification

Dana Class:

2.12.13.3 (2)Sulfides - Including Selenides and Tellurides

(2.12)where Am Bn Xp, with (m+n):p=1:2

(2.12.13)Dana Group

2.12.13.1 Krennerite AuTe2 Pma2 mm2

2.12.13.2 Calaverite AuTe2 C 2/m 2/m

2.12.13.3 Sylvanite (Au,Ag)2Te4 P 2/c 2/m

2.12.13.4 Kostovite CuAuTe4 Pma2 mm2

Strunz Class:

II/D.16-20 II - Sulfides and sulphosalts

II/D - Sulfides with metal: sulfur, selenium and tellurium < 1:1, Tellurides with Copper, Silver, Gold

II/D.16 - Kostovite - Calaverite series

II/D.16-10 Kostovite CuAuTe4 Pma2 mm2

II/D.16-20 Sylvanite (Au,Ag)2Te4 P 2/c 2/m

II/D.16-30 Krennerite AuTe2 Pma2 mm2

II/D.16-40 Calaverite AuTe2 C 2/m 2/m

Other Sylvanite Information

References:

NAME( AntBidBlaNic1) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic1)

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Print or Cut-and-Paste your Sylvanite Specimen Label here :

Sylvanite

(Au,Ag)2Te4
Dana No: 2.12.13.3 Strunz No: II/D.16-20
Locality:

Notes: