Geffroyite Mineral Data

Geffroyite Mineral Data +

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General Geffroyite Information

Chemical Formula:

(Ag,Cu,Fe)9(Se,S)8

Composition:

Molecular Weight = 1,342.22 gm

Iron 3.74 % Fe

Copper 12.78 % Cu

Silver 43.40 % Ag

Selenium 35.30 % Se

Sulfur 4.78 % S

______

100.00 %

Empirical Formula:

Ag_5.4Cu_2.7Fe²⁺_0.9Se₆S₂

Environment:

As late stage deposits in veins cutting granite. Micro-myrmikitic texture intergrowth with clausthalite and eskebornite.

IMA Status:

Approved IMA 1982

Locality:

From Chameane, Puy-de-Dome, France. Link to MinDat.org Location Data.

Name Origin:

To honor Jaques Geffroy, metallugist for the French Atomic Energy Commission.

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Geffroyite Crystallography

Cell Dimensions:

a = 10.889, Z = 3; V = 1,291.11 Den(Calc)= 5.18

Crystal System:

Isometric - HexoctahedralH-M Symbol (4/m 3 2/m) Space Group: F m3m

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

By Intensity(I/I_o): 1.925(1), 3.145(0.9), 3.282(0.9),

Physical Properties of Geffroyite

Color:

Bronze brown.

Density:

5.39

Diaphaniety:

Opaque

Hardness:

2.5 - Finger Nail

Luster:

Metallic

Optical Properties of Geffroyite

RL Color:

Brown with a creamy tint.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Geffroyite in Air**
λ	R	∑ R(λ)
420 nm	19.00
440 nm	21.40
460 nm	23.50
480 nm	25.50
500 nm	27.50
520 nm	29.10
540 nm	30.10
560 nm	31.70
580 nm	32.70
600 nm	33.60
620 nm	34.40
640 nm	35.10
660 nm	35.80
680 nm	36.30
700 nm	36.90

**Calculated Relative Intensity Colors of Geffroyite in Air**
Relative Intensity	0%	40%	80%	100%	120%	160%	200%	240%	280%	320%	360%	390%
R

Calculated Properties of Geffroyite

Electron Density:

r_electron=4.57 gm/cc
note: r_Geffroyite=5.18 gm/cc.

Fermion Index

Fermion Index = 0.02797
Boson Index = 0.97203

Photoelectric:

PE_Geffroyite= 147.93 barns/electron
U=PE_Geffroyite x r_electron= 675.39 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Geffroyite is Not Radioactive

Geffroyite Classification

Dana Class:

2.7.1.6 (2)Sulfides - Including Selenides and Tellurides

(2.7)where Am Bn Xp, with (m+n):p=9:8

(2.7.1)Pentalndite Group (Isometric: Fm3m)

2.7.1.1 Pentlandite (Fe,Ni)9S8 F m3m 4/m 3 2/m

2.7.1.2 Argentopentlandite Ag(Fe,Ni)8S8 F m3m 4/m 3 2/m

2.7.1.3 Cobaltpentlandite Co9S8 F m3m 4/m 3 2/m

2.7.1.4 Shadlunite (Pb,Cd)(Fe,Cu)8S8 F m3m 4/m 3 2/m

2.7.1.5 Manganese-shadlunite (Mn,Pb)(Cu,Fe)8S8 F m3m 4/m 3 2/m

2.7.1.6 Geffroyite (Ag,Cu,Fe)9(Se,S)8 F m3m 4/m 3 2/m

Strunz Class:

II/B.16-40 II - Sulfides and sulphosalts

II/B - Sulfides with metal: sulfur, selenium and tellurium > 1:1, Sulfides with predominant Nickel, Cobalt, Rhodium and Palladium

II/B.16 - Pentlandite group

II/B.16-10 Pentlandite (Fe,Ni)9S8 F m3m 4/m 3 2/m

II/B.16-20 Cobaltpentlandite Co9S8 F m3m 4/m 3 2/m

II/B.16-30 Argentopentlandite Ag(Fe,Ni)8S8 F m3m 4/m 3 2/m

II/B.16-40 Geffroyite (Ag,Cu,Fe)9(Se,S)8 F m3m 4/m 3 2/m

II/B.16-50 Manganese-shadlunite (Mn,Pb)(Cu,Fe)8S8 F m3m 4/m 3 2/m

II/B.16-60 Shadlunite (Pb,Cd)(Fe,Cu)8S8 F m3m 4/m 3 2/m

II/B.16-70 Palladseite Pd17Se15 P m3m 4/m 3 2/m

II/B.16-80 Miassite! Rh17S15 P m3m 4/m 3 2/m

II/B.16-80* Prassoite! Rh17S15(?) P m3m 4/m 3 2/m

Other Geffroyite Information

References:

NAME( AntBidBlaNic1) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic1)

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Geffroyite

(Ag,Cu,Fe)9(Se,S)8
Dana No: 2.7.1.6 Strunz No: II/B.16-40
Locality:

Notes: