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Selenopolybasite
A valid IMA mineral species
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About Selenopolybasite
Formula:
[(Ag,Cu)6(Sb,As)2(S,Se)7][Ag9Cu(S,Se)2Se2]
Colour:
Back
Lustre:
Metallic
Hardness:
3 - 3½
Specific Gravity:
6.548 (Calculated)
Crystal System:
Trigonal
Member of:
Name:
Selenium analogue of polybasite.
Unique Identifiers
Mindat ID:
31645
Long-form identifier:
mindat:1:1:31645:7
IMA Classification of Selenopolybasite
Approved
IMA Formula:
Cu1+(Ag1+,Cu1+)6Ag1+9Sb3+2(S2-,Se2-)9Se2-2
Approval year:
2006
First published:
2007
Type description reference:
Classification of Selenopolybasite
2.GB.15
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
G : Sulfarsenites, sulfantimonites, sulfbismuthites
B : Neso-sulfarsenites, etc. with additional S
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
G : Sulfarsenites, sulfantimonites, sulfbismuthites
B : Neso-sulfarsenites, etc. with additional S
3.1.7.2
3 : SULFOSALTS
1 : ø > 4
3 : SULFOSALTS
1 : ø > 4
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 |
|---|---|---|
| Splb | 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 Selenopolybasite
Metallic
Transparency:
Opaque
Colour:
Back
Streak:
Black
Hardness:
3 - 3½ on Mohs scale
Hardness:
VHN100=125 - 141 kg/mm2 - Vickers
Tenacity:
Brittle
Cleavage:
None Observed
Fracture:
None observed
Density:
6.548 g/cm3 (Calculated)
Comment:
Could not be measured due to small grain size
Optical Data of Selenopolybasite
Bireflectance:
Weak to moderate
Reflectivity:
| Wavelength | R1 (%) | R2 (%) |
|---|---|---|
| 471nm | 32.8% | 34.1% |
| 548nm | 31.0% | 32.9% |
| 586nm | 30.2% | 31.8% |
| 652nm | 29.3% | 30.0% |
Graph shows reflectance levels at different wavelengths (in nm). Peak reflectance is 34.1%.
R1 shown in black, R2 shown in red
Colour in reflected light:
Light gray
Internal Reflections:
None
Pleochroism:
Weak
Comments:
Grey to a violet-blue grey
Chemistry of Selenopolybasite
Mindat Formula:
[(Ag,Cu)6(Sb,As)2(S,Se)7][Ag9Cu(S,Se)2Se2]
Element Weights:
Crystallography of Selenopolybasite
Polytype:
Formula:
Crystal System:
Class (H-M)
Space Group:
Space Group Setting:
Cell Parameters:
Ratio:
Unit Cell Volume (calc):
Z:
Comment:
| Selenopolybasite-Tac |
|---|
| [(Ag,Cu)6(Sb,As)2(S,Se)7][Ag9Cu(S,Se)2Se2] |
| Trigonal |
| 3m(32/m) - Hexagonal Scalenohedral |
| P3m1 |
| a = 7.5950(4) Å, c = 12.0731(6) Å |
| a:c = 1 : 1.59 |
| V 603.12 ų (Calculated from Unit Cell) |
| 1 |
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.1731 Å | (48) |
| 3.0183 Å | (84) |
| 2.8880 Å | (100) |
| 2.5466 Å | (23) |
| 2.3629 Å | (34) |
| 2.2237 Å | (28) |
| 1.8987 Å | (31) |
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 Selenopolybasite
General Appearance of Type Material:
Black anhedral to subhedral grains up to 400 µm across.
Place of Conservation of Type Material:
Mineralogical Collection of the Museo di Storia Naturale, Università di Firenze, Italy, under the catalogue number 2453/I.
Geological Setting of Type Material:
A selenide deposit in siliceous veins in a rhyolite porphyry.
Associated Minerals at Type Locality:
Synonyms of Selenopolybasite
Other Language Names for Selenopolybasite
Relationship of Selenopolybasite to other Species
Member of:
Other Members of Pearceite-Polybasite Group:
| Argentopearceite | [Ag6As2S7][Ag9AgS4] | Trig. 32 : P321 |
| Argentopolybasite | [Ag6Sb2S7][Ag9AgS4] | Trig. 32 : P321 |
| 'Argentopolybasite-T2ac' | Ag16Sb2S11 | Trig. 32 : P321 |
| Auropearceite | [Ag6As2S7][Ag9AuS4] | Trig. 32 : P321 |
| Auropolybasite | [Ag6Sb2S7][Ag9AuS4] | Trig. 32 : P321 |
| Benleonardite | [Ag6(Sb,As)2S6Te][Ag9Cu(S,Te)2Te2] | Trig. 3m(32/m) : P3m1 |
| Cupropearceite | [Cu6As2S7][Ag9CuS4] | Trig. 3m(32/m) : P3m1 |
| Cupropolybasite | [Cu6Sb2S7][Ag9CuS4] | Trig. 3m : P31m |
| Fengruiite | [Ag6Sb2S7][Ag9CuS2Te2] | Trig. 3m(32/m) : P3m1 |
| Pearceite | [Ag6As2S7][Ag9CuS4] | Trig. 3m(32/m) : P3m1 |
| Polybasite | [Ag6Sb2S7][Ag9CuS4] | Mon. 2/m : B2/m |
Common Associates
Associations Based on Photo Data:
| 2 photos of Selenopolybasite associated with Naumannite | Ag2Se |
Related Minerals - Strunz-mindat Grouping
| 2.GB. | 'Polybasite-Tac' | [Ag6Sb2S7][Ag9CuS4] |
| 2.GB. | Kenoargentotetrahedrite-(Zn) | [Ag6]4+(Cu4Zn2)Sb4S12◻ |
| 2.GB. | Argentotetrahedrite-(Hg) | Ag6(Cu4Hg2)Sb4S12S |
| 2.GB. | Annivite-(Zn) | Cu6(Cu4Zn2)Bi4S12S |
| 2.GB. | Pošepnýite | (Cu+3◻3)(Hg2+4Cu+2)Sb4Se12(Se0.5◻0.5) |
| 2.GB. | Tennantite-(Cu) | Cu6(Cu4Cu2)As4S12S |
| 2.GB. | Argentopolybasite | [Ag6Sb2S7][Ag9AgS4] |
| 2.GB. | Tennantite-(Mn) | Cu6(Cu4Mn2)As4S12S |
| 2.GB. | Argentotetrahedrite-(Cd) | Ag6(Cu4Cd2)Sb4S12S |
| 2.GB. | Stibioústalečite | (Cu4Cu2)(Cu4Cu+2)(Sb2Te2)Se12Se |
| 2.GB. | Stibiogoldfieldite | (Cu4Cu2)(Cu4Cu+2)(Sb2Te2)S12S |
| 2.GB. | Argentotetrahedrite-(Zn) | Ag6(Cu4Zn2)Sb4S12S |
| 2.GB. |
De Lamar Mine, De Lamar Mining District, Owyhee County, Idaho, USA