Muthmannite Mineral Data

Muthmannite Mineral Data +

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General Muthmannite Information

Chemical Formula:

AgAuTe2

Composition:

Molecular Weight = 556.88 gm

Silver 19.18 % Ag

Tellurium 46.51 % Te

Gold 34.31 % Au

______

100.00 %

Empirical Formula:

Au_0.97Ag_0.99Te_2.03

Environment:

In close intergrowths with other tellurides, especially krennerite, in epithermal hydorthermal veins and in ores enriched by secondary processes.

IMA Status:

Valid Species (Pre-IMA) 1911

Locality:

Sacaramb, Romania. Link to MinDat.org Location Data.

Name Origin:

Named for Friedrich W. Muthmann (1861-1913), German chemist and crystallographer.

Muthmannite Image

Images:

Muthmannite

Comments: Backscattered scanning electron microphotograph of muthmannite (light gray) rimming a sylvanite (dark gray) grain. (AmMin 89:1506).
Location: Museum specimen from a gold-telluride deposit of Sacar?mb, Metaliferi Mountains, western Romania.. Scale: See Image.
© American Mineralogist

Muthmannite Crystallography

Axial Ratios:

a:b:c =1.1595:1:1.6829

Cell Dimensions:

a = 5.124, b = 4.419, c = 7.437, Z = 2; beta = 89.96° V = 168.40 Den(Calc)= 10.98

Crystal System:

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

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

By Intensity(I/I_o): 3.03(1), 2.11(0.8), 2.94(0.5),1.04(0.3), 1.32(0.3), 1.7(0.3), 1.95(0.3), 5.09(0.2),

Crystal Structure:

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Bindi L , Cipriani C , American Mineralogist , 89 (2004) p.1505-1509, Ordered distribution of Au and Ag in the crystal structure of muthmannite,, AuAgTe2, a rare telluride from Sacarimb, Western Romania

Physical Properties of Muthmannite

Cleavage:

[???] Perfect

Color:

Blackish yellow, Bronzy yellow, Grayish white.

Diaphaniety:

Opaque

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Habit:

Tabular - Form dimensions are thin in one direction.

Hardness:

2.5 - Finger Nail

Luminescence:

Non-fluorescent.

Luster:

Metallic

Magnetism:

Nonmagnetic

Streak:

black

Optical Properties of Muthmannite

RL Anisotrophism:

Distinct.

RL Bireflectance:

Very low.

RL Color:

Grayish white with no internal reflections.

RL Pleochroism:

Very low.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Muthmannite in Air**
λ	R₁	R₂	∑ R₁(λ)	∑ R₂(λ)
470 nm	40.10	40.80
550 nm	38.30	38.60
589 nm	37.90	38.30
650 nm	37.70	38.10

**Calculated Relative Intensity Colors of Muthmannite in Air**
Relative Intensity	0%	30%	60%	90%	100%	120%	150%	180%	210%	240%
R₁
R₂

Calculated Properties of Muthmannite

Electron Density:

r_electron=9.02 gm/cc
note: r_Muthmannite=11.0 gm/cc.

Fermion Index

Fermion Index = 0.03716
Boson Index = 0.96284

Photoelectric:

PE_Muthmannite= 795.07 barns/electron
U=PE_Muthmannite x r_electron=7,171.06 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Muthmannite is Not Radioactive

Muthmannite Classification

Dana Class:

2.8.25.1 (2)Sulfides - Including Selenides and Tellurides

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

(2.8.25)Dana Group

2.8.25.1 Muthmannite AgAuTe2 P 2/m Ortho

Strunz Class:

II/B.07-70 II - Sulfides and sulphosalts

II/B - Sulfides with metal: sulfur, selenium and tellurium > 1:1, Sulfides, Selenides and Tellurides with predominant Copper and Silver/Gold

II/B.07 - Petrovskaite - Muthmannite series

II/B.07-10 Petrovskaite AuAg(S,Se) P 2/m,P 2,Pm Mono

II/B.07-20 Uytenbogaardtite Ag3AuS2 P 4₁22 4 2 2

II/B.07-30 Criddleite TlAg2Au3Sb10S10 A2/m ? 2/m

II/B.07-40 Penzhinite (Ag,Cu)4Au(S,Se)4 P 6₃22 6 2 2

II/B.07-50 Fischesserite Ag3AuSe2 I 4₁32 4 3 2

II/B.07-60 Petzite Ag3AuTe2 I 4₁32 4 3 2

II/B.07-70 Muthmannite AgAuTe2 P 2/m Ortho

Other Muthmannite Information

References:

NAME( Dana8) PHYS. PROP.(Dana, AmMin, 89:1505) OPTIC PROP.(AmMin, 89:1505)

See Also:

Links to other databases for Muthmannite :
1 -Am. Min. Crystal Structure Database 2 -Athena 3 - EUROmin Project 4 -Google Images 5 -Google Scholar 6 -Handbook of Mineralogy (UofA) 7 -MinDAT 8 -MinMax(Deutsch) 9 -MinMax(English) 10 -Mineralienatlas (Deutsch) 11 -QUT Mineral Atlas 12 -École des Mines de Paris

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Muthmannite

AgAuTe2
Dana No: 2.8.25.1 Strunz No: II/B.07-70
Locality:

Notes: