Geffroyite
A valid IMA mineral species
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About Geffroyite
Jacques Geffroy
Formula:
(Cu,Fe,Ag)9(Se,S)8
Lustre:
Metallic
Hardness:
2½
Specific Gravity:
5.39 (Calculated)
Crystal System:
Isometric
Member of:
Name:
Named in honor of Jacques Geffroy (1918–1993), French geologist and metallurgist at the French Atomic Energy Commission. He published many books and articles for the general public.
This page provides mineralogical data about Geffroyite.
Unique Identifiers
Mindat ID:
1667
Long-form identifier:
mindat:1:1:1667:0
GUID
(UUID V4):
(UUID V4):
8db72961-ee81-4dca-b07e-0ab75dd1e789
IMA Classification of Geffroyite
Classification of Geffroyite
2.BB.15
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
B : Metal Sulfides, M: S > 1: 1 (mainly 2: 1)
B : With Ni
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
B : Metal Sulfides, M: S > 1: 1 (mainly 2: 1)
B : With Ni
2.7.1.6
2 : SULFIDES
7 : AmBnXp, with (m+n):p = 9:8
2 : SULFIDES
7 : AmBnXp, with (m+n):p = 9:8
3.2.18
3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
2 : Sulphides etc. of Ag
3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
2 : Sulphides 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 |
|---|---|---|
| Gef | 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 Geffroyite
Metallic
Transparency:
Opaque
Hardness:
2½ on Mohs scale
Hardness:
VHN15=67 - 72 kg/mm2 - Vickers
Density:
5.39 g/cm3 (Calculated)
Optical Data of Geffroyite
Reflectivity:
| Wavelength | R |
|---|---|
| 420nm | 19.0% |
| 440nm | 21.4% |
| 460nm | 23.5% |
| 480nm | 25.5% |
| 500nm | 27.5% |
| 520nm | 29.1% |
| 540nm | 30.1% |
| 560nm | 31.7% |
| 580nm | 32.7% |
| 600nm | 33.6% |
| 620nm | 34.4% |
| 640nm | 35.1% |
| 660nm | 35.8% |
| 680nm | 36.3% |
| 700nm | 36.9% |
Graph shows reflectance levels at different wavelengths (in nm). Top of box is 100%. Peak reflectance is 36.9%.
Colour in reflected light:
Brown with creamy tint
Chemistry of Geffroyite
Mindat Formula:
(Cu,Fe,Ag)9(Se,S)8
Crystallography of Geffroyite
Crystal System:
Isometric
Class (H-M):
m3m (4/m 3 2/m) - Hexoctahedral
Space Group:
Fm3m
Setting:
Fm3m
Cell Parameters:
a = 10.889 Å
Unit Cell V:
1,291.11 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Micro myrmekitic intergrowth with clausthalite and eskebornite.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 1.925 Å | (100) |
| 3.282 Å | (90) |
| 3.145 Å | (90) |
| 2.094 Å | (60) |
| 1.112 Å | (60) |
| 1.660 Å | (50) |
| 2.436 Å | (40) |
Comments:
Chaméane mine, France. Data from the type description.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-𝑇 alteration and/or metamorphism | |
| 33 : Minerals deposited by hydrothermal metal-rich fluids (see also [#12]) |
Type Occurrence of Geffroyite
General Appearance of Type Material:
Very fine-grained intergrowth (0.2-0.7 mm) with other selenides.
Place of Conservation of Type Material:
National School of Mines, Paris, France, number 54615 (holotype).
Geological Setting of Type Material:
Late stage veins cutting granite.
Associated Minerals at Type Locality:
Synonyms of Geffroyite
Other Language Names for Geffroyite
German:Geffroyit
Spanish:Geffroyita
Relationship of Geffroyite to other Species
Member of:
Other Members of this group:
| Argentopentlandite | Ag(Fe,Ni)8S8 | Iso. m3m (4/m 3 2/m) : Fm3m |
| Cobaltpentlandite | Co9S8 | Iso. m3m (4/m 3 2/m) : Fm3m |
| Oberthürite | Rh3Ni32S32 | Iso. |
| Pentlandite | (NixFey)Σ9S8 | Iso. m3m (4/m 3 2/m) : Fm3m |
| Shadlunite | (Pb,Cd)(Fe,Cu)8S8 | Iso. m3m (4/m 3 2/m) : Fm3m |
| Sugakiite | Cu(Fe,Ni)8S8 | Tet. 4/mmm (4/m 2/m 2/m) : P42/mnm |
Common Associates
Associated Minerals Based on Photo Data:
| 3 photos of Geffroyite associated with Eskebornite | CuFeSe2 |
| 3 photos of Geffroyite associated with Uraninite | UO2 |
| 1 photo of Geffroyite associated with Fischesserite | Ag3AuSe2 |
Related Minerals - Strunz-mindat Grouping
| 2.BB. | Horomanite | Fe6Ni3S8 |
| 2.BB. | Samaniite | Cu2Fe5Ni2S8 |
| 2.BB. | UM2007-27-S:CuFeIrNiRh | (Ni,Fe,Cu,Rh,Ir)11S9 |
| 2.BB. | Arsenotučekite | Ni18Sb3AsS16 |
| 2.BB. | Hrabákite | Ni9PbSbS8 |
| 2.BB.05 | Heazlewoodite | Ni3S2 |
| 2.BB.05 | Oregonite | Ni2FeAs2 |
| 2.BB.05 | Vozhminite | (Ni,Co)4(As,Sb)S2 |
| 2.BB.05 | UM2007-30-S:Fe | Fe3S2 |
| 2.BB.10 | Arsenohauchecornite | Ni18Bi3AsS16 |
| 2.BB.10 | Bismutohauchecornite | Ni9Bi2S8 |
| 2.BB.10 | Hauchecornite | Ni9BiSbS8 |
| 2.BB.10 | Tellurohauchecornite | Ni9Bi(Te,Bi)S8 |
| 2.BB.10 | Tučekite | Ni9Sb2S8 |
| 2.BB.15 | Argentopentlandite | Ag(Fe,Ni)8S8 |
| 2.BB.15 | Cobaltpentlandite | Co9S8 |
| 2.BB.15 | Godlevskite | (Ni,Fe)9S8 |
| 2.BB.15 | Kharaelakhite | (Cu,Pt,Pb,Fe,Ni)9S8 |
| 2.BB.15 | Manganoshadlunite | (Mn,Pb,Cd)(Cu,Fe)8S8 |
| 2.BB.15 | Pentlandite | (NixFey)Σ9S8 |
| 2.BB.15 | Shadlunite | (Pb,Cd)(Fe,Cu)8S8 |
| 2.BB.15 | Sugakiite | Cu(Fe,Ni)8S8 |
| 2.BB.15 | UM2002-26-S:FeNi | (Ni,Fe)9S8 |
| 2.BB.15 | Ferhodsite | (Fe,Rh,Ni,Ir,Cu,Pt)9S8 |
| 2.BB.15 | Oberthürite | Rh3Ni32S32 |
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 Geffroyite
mindat.org URL:
https://www.mindat.org/min-1667.html
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References for Geffroyite
Localities for Geffroyite
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.
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Chaméane Uranium Deposit, Le Vernet-Chaméane, Issoire, Puy-de-Dôme, Auvergne-Rhône-Alpes, France