Trechmannite
A valid IMA mineral species - grandfathered
This page is currently not sponsored. Click here to sponsor this page.
About Trechmannite
Charles Otto Trechmann (1851-1917)
Formula:
AgAsS2
Colour:
Deep vermilion-red
Lustre:
Adamantine
Hardness:
1½ - 2
Specific Gravity:
4.77 (Calculated)
Crystal System:
Trigonal
Name:
Named after Charles Otto Trechmann (19 March 1851, Hartlepool, England - 29 June 1917), English cement mill owner and spare-time crystallographer.
Type Locality:
Dimorph of:
This page provides mineralogical data about Trechmannite.
Unique Identifiers
Mindat ID:
4009
Long-form identifier:
mindat:1:1:4009:5
Similar Names
IMA Classification of Trechmannite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Ag1+As3+S2-2
First published:
1905
Classification of Trechmannite
2.GC.35
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
G : Sulfarsenites, sulfantimonites, sulfbismuthites
C : Poly-sulfarsenites
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
G : Sulfarsenites, sulfantimonites, sulfbismuthites
C : Poly-sulfarsenites
3.7.2.1
3 : SULFOSALTS
7 : ø = 2
3 : SULFOSALTS
7 : ø = 2
5.2.2
5 : Sulphosalts - Sulpharsenites and Sulphobismuthites (those containing Sn, Ge,or V are in Section 6)
2 : Sulpharsenites etc. of Ag
5 : Sulphosalts - Sulpharsenites and Sulphobismuthites (those containing Sn, Ge,or V are in Section 6)
2 : Sulpharsenites etc. of Ag
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 |
|---|---|---|
| Trh | 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 Trechmannite
Adamantine
Transparency:
Transparent, Translucent
Colour:
Deep vermilion-red
Streak:
Scarlet red
Hardness:
1½ - 2 on Mohs scale
Hardness:
VHN25=97 - 100 kg/mm2 - Vickers
Tenacity:
Brittle
Cleavage:
Distinct/Good
Good on {1011}, distinct on {0001}
Good on {1011}, distinct on {0001}
Fracture:
Conchoidal
Density:
4.77 g/cm3 (Calculated)
Comment:
Calculated on synthetic material
Optical Data of Trechmannite
Type:
Uniaxial (-)
RI values:
nω = 2.6 nε = 2.4
Max. Birefringence:
δ = 0.200
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Very High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized uniaxial interference figure - the conoscopic
(convergent-light, Bertrand-lens-in) view, for a grain cut with the optic axis
centred and vertical. The coloured rings are isochromatics, computed with the
same physics as the Michel-Lévy bar above; the dark cross is the isogyre.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
Bireflectance:
Extreme
Reflectivity:
| Wavelength | R1 (%) | R2 (%) |
|---|---|---|
| 400nm | 26.2% | 37.6% |
| 420nm | 25.7% | 36.9% |
| 440nm | 24.9% | 35.5% |
| 460nm | 23.7% | 33.8% |
| 480nm | 23.0% | 32.6% |
| 500nm | 23.4% | 31.6% |
| 520nm | 23.7% | 30.7% |
| 540nm | 23.4% | 29.9% |
| 560nm | 22.7% | 29.1% |
| 580nm | 22.1% | 28.5% |
| 600nm | 21.5% | 28.0% |
| 620nm | 21.0% | 27.6% |
| 640nm | 20.6% | 27.2% |
| 660nm | 20.3% | 26.9% |
| 680nm | 20.0% | 26.4% |
| 700nm | 19.9% | 26.2% |
Graph shows reflectance levels at different wavelengths (in nm). Peak reflectance is 37.6%.
R1 shown in black, R2 shown in red
Colour in reflected light:
Scarlet-vermilion with bluish cast
Internal Reflections:
Red-orange
Pleochroism:
Weak
Comments:
Faint with O = pale reddish, E = clear and nearly colorless
Chemistry of Trechmannite
Mindat Formula:
AgAsS2
Element Weights:
Elements listed:
Crystallography of Trechmannite
Crystal System:
Trigonal
Class (H-M):
3 - Rhombohedral
Space Group:
R3
Cell Parameters:
a = 13.98 Å, c = 9.12 Å
Ratio:
a:c = 1 : 0.652
Unit Cell V:
1,543.62 ų (Calculated from Unit Cell)
Z:
18
Morphology:
Short prismatic, equant. Sometimes irregular.
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Display Options
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
View
CIF File Best | x | y | z | a | b | c
CIF File Best | x | y | z | a | b | c
Rotation
Stop | Start
Stop | Start
Labels
Console Off | On | Grey | Yellow
Console Off | On | Grey | Yellow
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) |
|---|---|---|---|---|---|---|---|
| 0010682 | Trechmannite | Matsumoto T, Nowacki W (1969) The crystal structure of trechmannite, AgAsS2 Zeitschrift fur Kristallographie 129 163-177 |  | 1969 | Lengenbach quarry, Binnatal, Canton Wallis, Switzerland | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.702 Å | (100) |
| 3.15 Å | (80) |
| 1.887 Å | (80) |
| 1.937 Å | (70) |
| 7.0 Å | (60) |
| 4.26 Å | (60) |
| 3.64 Å | (60) |
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 Trechmannite
General Appearance of Type Material:
Minute red crystals resting on a crystal of baumhauerite in a cavity in white dolomite.
Place of Conservation of Type Material:
Natural History Museum, London, United Kingdom (number of the type
specimen is lacking).
specimen is lacking).
Associated Minerals at Type Locality:
Synonyms of Trechmannite
Other Language Names for Trechmannite
Common Associates
Associations Based on Photo Data:
| 7 photos of Trechmannite associated with Billingsleyite | Ag7AsS6 |
| 6 photos of Trechmannite associated with Realgar | As4S4 |
| 5 photos of Trechmannite associated with Calcite | CaCO3 |
| 4 photos of Trechmannite associated with Dolomite | CaMg(CO3)2 |
| 3 photos of Trechmannite associated with Aktashite | Cu6Hg3As4S12 |
| 3 photos of Trechmannite associated with Proustite | Ag3AsS3 |
| 3 photos of Trechmannite associated with Acanthite | Ag2S |
| 2 photos of Trechmannite associated with Pyrite | FeS2 |
| 2 photos of Trechmannite associated with Wallisite | (Cu,Ag)TlPbAs2S5 |
| 2 photos of Trechmannite associated with Hatchite | AgTlPbAs2S5 |
Related Minerals - Strunz-mindat Grouping
| 2.GC.05 | Hatchite | AgTlPbAs2S5 |
| 2.GC.05 | Wallisite | (Cu,Ag)TlPbAs2S5 |
| 2.GC.10 | Sinnerite | Cu6As4S9 |
| 2.GC.15 | Watanabeite | Cu4(As,Sb)2S5 |
| 2.GC.20 | Simonite | TlHgAs3S6 |
| 2.GC.25 | Quadratite | Ag(Cd,Pb)AsS3 |
| 2.GC.25 | Manganoquadratite | AgMnAsS3 |
| 2.GC.30 | Smithite | AgAsS2 |
| 2.GC.35 | Debattistiite | Ag9Hg0.5As6S12Te2 |
| 2.GC.40a | Aleksite | PbBi2Te2S2 |
| 2.GC.40d | Saddlebackite | Pb2Bi2Te2S3 |
| 2.GC.40c | Rucklidgeite | PbBi2Te4 |
| 2.GC.40 | Clogauite | PbBi4Te4S3 |
| 2.GC.40e | Babkinite | Pb2Bi2(S,Se)3 |
| 2.GC.40b | Kochkarite | PbBi4Te7 |
| 2.GC.40c | Poubaite | PbBi2(Se,Te,S)4 |
| 2.GC.45 | Tvalchrelidzeite | Hg3SbAsS3 |
| 2.GC.50 | Mutnovskite | Pb4As2S6ICl |
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.
Internet Links for Trechmannite
mindat.org URL:
https://www.mindat.org/min-4009.html
Please feel free to link to this page.
Please feel free to link to this page.
Search Engines:
External Links:
Mineral Dealers:
References for Trechmannite
Reference List:
Solly, R. H. (1905) Some new minerals from the Binnenthal, Switzerland. Mineralogical Magazine and Journal of the Mineralogical Society, 14 (64) 72-82 doi:10.1180/minmag.1905.014.64.03
Herbert Smith, G. F., Prior, G. T. (1907) Red silver minerals from the Binnenthal, Switzerland. Mineralogical Magazine and Journal of the Mineralogical Society, 14 (67) 283-307 doi:10.1180/minmag.1907.014.67.02
Matsumoto, Takeo, Nowacki, Werner (1969) The crystal structure of trechmannite, AgAsS2. Zeitschrift für Kristallographie, 129 (1). 163-177 doi:10.1524/zkri.1969.129.1-4.163
Kharbish, S. (2017) Spectral-structural characteristics of the extremely scarce silver arsenic sulfosalts, proustite, smithite, trechmannite and xanthoconite: μ-Raman spectroscopy evidence. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 177. 104-110 doi:10.1016/j.saa.2017.01.038
Localities for Trechmannite
Showing 10 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Australia | |
| A. R. Seymon |
Austria | |
| Kolitsch et al. (2017) |
Germany | |
| From the Wilke collection. +1 other reference |
Iran | |
| Topa et al. (2013) |
New Zealand | |
| Moore (1979) |
| Moore (1979) | |
Peru | |
| Frank Keutsch collection |
Romania | |
| Dincă et al. (2025) |
Switzerland (TL) | |
| Solly (1905) +1 other reference |
| 50. (in German) +1 other reference |
Quick NavTopAbout TrechmanniteUnique IdentifiersSimilar NamesIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatOther InformationInternet Links References Localities Locality List
Lengenbach Quarry, Fäld, Binn, Goms, Valais, Switzerland