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Muthmannite
A valid IMA mineral species - grandfathered
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About Muthmannite
F. Wilhelm Muthmann
Formula:
AuAgTe2
Colour:
Brassy yellow to pale bronze
Lustre:
Metallic
Hardness:
2½
Specific Gravity:
11.04 (Calculated)
Crystal System:
Monoclinic
Name:
Named in honor of Friedrich Wilhelm Muthmann (8 February 1861, Elberfeld - 3 August 1913, Munich), German chemist and crystallographer, and professor at Technische Hochschule, Munich.
Type Locality:
Originally described as (Ag,Au)Te, recently redefined as AuAgTe2 (Bindi & Cipriani, 2004).
Unique Identifiers
Mindat ID:
2819
Long-form identifier:
mindat:1:1:2819:2
IMA Classification of Muthmannite
Approved, 'Grandfathered' (first described prior to 1959)
First published:
1911
Classification of Muthmannite
2.CB.85
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
C : Metal Sulfides, M: S = 1: 1 (and similar)
B : With Zn, Fe, Cu, Ag, etc.
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
C : Metal Sulfides, M: S = 1: 1 (and similar)
B : With Zn, Fe, Cu, Ag, etc.
2.8.26.
2 : SULFIDES
8 : AmXp, with m:p = 1:1
2 : SULFIDES
8 : AmXp, with m:p = 1:1
3.3.8
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
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
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Mma | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Muthmannite
Metallic
Transparency:
Opaque
Colour:
Brassy yellow to pale bronze
Comment:
pale gray on fresh fracture
Streak:
Black to gray-black
Hardness:
2½ on Mohs scale
Hardness:
VHN15=194 kg/mm2 - Vickers
Cleavage:
Perfect
in zone of elongation
in zone of elongation
Fracture:
Irregular/Uneven
Density:
11.04 g/cm3 (Calculated)
Optical Data of Muthmannite
Anisotropism:
Very weak
Bireflectance:
very low
Reflectivity:
| Wavelength | R1 (%) |
|---|---|
| 420nm | 42.3% |
| 440nm | 41.3% |
| 460nm | 40.4% |
| 480nm | 39.7% |
| 500nm | 39.2% |
| 520nm | 38.7% |
| 540nm | 38.4% |
| 560nm | 38.2% |
| 580nm | 38.1% |
| 600nm | 38.0% |
| 620nm | 38.0% |
| 640nm | 38.0% |
| 660nm | 38.1% |
| 680nm | 38.2% |
| 700nm | 38.4% |
Graph shows reflectance levels at different wavelengths (in nm). Peak reflectance is 42.3%.
Colour in reflected light:
pale gray
Pleochroism:
Weak
Comments:
very low
Chemistry of Muthmannite
Mindat Formula:
AuAgTe2
Elements listed:
Common Impurities:
Pb,Sb,S
Crystallography of Muthmannite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P2/m
Setting:
P2/m
Cell Parameters:
a = 5.124(2) Å, b = 4.419(1) Å, c = 7.437 Å
β = 89.96°
β = 89.96°
Ratio:
a:b:c = 1.16 : 1 : 1.683
Unit Cell V:
168.40 ų (Calculated from Unit Cell)
Z:
2
Comment:
some analogies to calaverite
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0003649 | Muthmannite | Bindi L, Cipriani C (2004) Ordered distribution of Au and Ag in the crystal structure of muthmannite, AuAgTe2, a rare telluride from Sacarimb, Western Romania American Mineralogist 89 1505-1509 |  | 2004 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 5.124 Å | (12) |
| 3.346 Å | (16) |
| 3.052 Å | (22) |
| 3.051 Å | (19) |
| 2.562 Å | (24) |
| 2.488 Å | (93) |
| 2.487 Å | (100) |
| 2.210 Å | (42) |
| 1.8592 Å | (22) |
| 1.5931 Å | (17) |
Comments:
From calculated pattern. Similar to the data for calaverite.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 33 : Minerals deposited by hydrothermal metal-rich fluids (see also [#12]) |
Type Occurrence of Muthmannite
Place of Conservation of Type Material:
University of Naples Museum, Naples, Italy.
Other Language Names for Muthmannite
Related Minerals - Strunz-mindat Grouping
| 2.CB. | Richardsite | Zn2CuGaS4 |
| 2.CB. | Okruginite | Cu2SnSe3 |
| 2.CB. | Hanswilkeite | KFeS2 |
| 2.CB. | Auroselenide | AuSe |
| 2.CB. | Ruizhongite | (Ag2◻)Pb3Ge2S8 |
| 2.CB. | Agmantinite | Ag2MnSnS4 |
| 2.CB. | Tolstykhite | Au3S4Te6 |
| 2.CB. | Gachingite | Au(Te1-xSex) |
| 2.CB.05a | Hawleyite | CdS |
| 2.CB.05 | 'UM1998-15-S:CuFeZn' | Cu2Fe3Zn5S10 |
| 2.CB.05a | Coloradoite | HgTe |
| 2.CB.05a | Metacinnabar | HgS |
| 2.CB.05a | Tiemannite | HgSe |
| 2.CB.05a | Sphalerite | ZnS |
| 2.CB.05b | Sakuraiite | (Cu,Zn,Fe)3(In,Sn)S4 |
| 2.CB.05c | Polhemusite | (Zn,Hg)S |
| 2.CB.05a | Rudashevskyite | (Fe,Zn)S |
| 2.CB.05a | Stilleite | ZnSe |
| 2.CB.05a | Ishiharaite | (Cu,Ga,Fe,In,Zn)S |
| 2.CB.07a | 'Unnamed (Cu-Mn-Sn Sulphide)' | Cu2MnSnS4 |
| 2.CB.07a | Shenzhuangite | NiFeS2 |
| 2.CB.10b | Talnakhite | Cu9(Fe,Ni)8S16 |
| 2.CB.10b | Haycockite | Cu4Fe5S8 |
| 2.CB.10a | Lenaite | AgFeS2 |
| 2.CB.10a | Gallite | CuGaS2 |
| 2.CB.10a | Roquesite | CuInS2 |
| 2.CB.10a | Eskebornite | CuFeSe2 |
| 2.CB.10a | 'UM1984-30-S:CuFeSn' | Cu2Fe2Sn3S7 |
| 2.CB.10c | Omariniite | Cu8Fe2ZnGe2S12 |
| 2.CB.10a | Chalcopyrite | CuFeS2 |
| 2.CB.10a | 'Unnamed (Cu-Zn-In Sulphide)' | CuZn2InS4 |
| 2.CB.10b | Mooihoekite | Cu9Fe9S16 |
| 2.CB.10a | Laforêtite | AgInS2 |
| 2.CB.10b | Putoranite | Cu1.1Fe1.2S2 |
| 2.CB.15a | Velikite | Cu2HgSnS4 |
| 2.CB.15c | 'UM2006-11-S:CuFeGeZn' | Cu8(Fe,Zn)3Ge2S12 (?) |
| 2.CB.15a | Hocartite | Ag2(Fe2+,Zn)SnS4 |
| 2.CB.15a | Kësterite | Cu2ZnSnS4 |
| 2.CB.15a | Pirquitasite | Ag2ZnSnS4 |
| 2.CB.15a | Stannite | Cu2FeSnS4 |
| 2.CB.15c | Stannoidite | Cu+6Cu2+2(Fe2+,Zn)3Sn2S12 |
| 2.CB.15b | Mohite | Cu2SnS3 |
| 2.CB.15a | Černýite | Cu2CdSnS4 |
| 2.CB.15a | Idaite | Cu5FeS6 |
| 2.CB.15a | Ferrokësterite | Cu2FeSnS4 |
| 2.CB.15a | Kuramite | Cu3SnS4 |
| 2.CB.17a v | 'Arsenic-bearing Renierite' | Cu11GeAsFe4S16 |
| 2.CB.20 | Mawsonite | Cu6Fe2SnS8 |
| 2.CB.20 | Chatkalite | Cu6FeSn2S8 |
| 2.CB.30 | 'Frieseite' | Ag2Fe5S8 (?) |
| 2.CB.30 | Nekrasovite | Cu26V2(Sn,As,Sb)6S32 |
| 2.CB.30 | 'Argyropyrite' | near Ag2Fe7S11 |
| 2.CB.30 | Maikainite | Cu20(Fe,Cu)6Mo2Ge6S32 |
| 2.CB.30 | Colusite | Cu13VAs3S16 |
| 2.CB.30 | Germanite | Cu13Fe2Ge2S16 |
| 2.CB.30 |
Săcărâmb, Certeju de Sus, Hunedoara County, Romania