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Laforêtite

Formula:
AgInS
 
2
System:TetragonalColour:Brown
Lustre:MetallicHardness:3
Name:Named for Claude P. Laforêt (b. 1936), metallographer at the Bureau de Recherches Géologiques et Minières, who first observed the mineral at the Montgros Mine.
This page provides mineralogical data about Laforêtite.

Classification of Laforêtite

IMA status:Approved 1995
Strunz 8th edition ID:2/C.03-45
Nickel-Strunz 10th (pending) edition ID:2.CB.10

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.
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Type Occurrence of Laforêtite

Type Locality:Montgros Mine, Pinols, Pinols, Haute-Loire, Auvergne, France
Geological Setting of type material:brecciated vein sample from the mine dump
Associated Minerals at type locality:
SphaleriteQuartzGalenaCalciteBaryte

Physical Properties of Laforêtite

Lustre:Metallic
Diaphaneity (Transparency):Opaque
Colour:Brown
Streak:Chocolate brown
Hardness (Mohs):3
Hardness (Vickers):VHN100=183 kg/mm2
Hardness Data:Estimated
Cleavage:None Observed
Density (calculated):4.92 g/cm3

Crystallography of Laforêtite

Crystal System:Tetragonal
Class (H-M):4 2m - Scalenohedral
Space Group:I4 2d
Cell Parameters:a = 5.88Å, c = 11.21Å
Ratio:a:c = 1 : 1.906
Unit Cell Volume:V 387.57 ų
Z:4
Twinning:Polysynthetic lamellar observed in polished sections.
X-Ray Powder Diffraction:
d-spacingIntensity
3.351 (100)
2.942 (80)
2.082 (75)
2.035 (75)
1.768 (80)
1.707 (35)
Comments:From synthetic material because of small size of grains.

Optical Data of Laforêtite

Type:Anisotropic
Anisotropism:Strong, brick red with orange tint to bluish-grey purplish
Reflectivity:
480nmR=26%
540nmR=24.6%
580nmR=24.2%
660nmR=25.8%


Graph shows reflectance levels at different wavelengths (in nm). Peak reflectance is 26%.
Colour in reflected light:Brownish grey
Pleochroism:Weak
Comments:Brown to clear brown-grey tints

Chemical Properties of Laforêtite

Formula:
AgInS
 
2
Essential elements:Ag, In, S
All elements listed in formula:Ag, In, S
Analyical Data:Means of eight sets of electron microprobe data
Cu (0.04)
Ag (37.68)
In (40.22)
Fe (0.02)
Se (0.01)
S (22.42)
Total: 100.39 wt.%
Empirical Formula:
Ag
 
1.00
In
 
1.00
S
 
2.00
Common Impurities:Cu,Fe,Se

Relationship of Laforêtite to other Species

Related Minerals - Nickel-Strunz Grouping):
2.CB.05Coloradoite
HgTe
2.CB.05Hawleyite
CdS
2.CB.05Metacinnabar
HgS
2.CB.05Polhemusite
(Zn,Hg)S
2.CB.05Sakuraiite
(Cu,Zn,Fe)
 
3
(In,Sn)S
 
4
2.CB.05Sphalerite
(Zn,Fe
2+
 
)S
2.CB.05Stilleite
ZnSe
2.CB.05Tiemannite
HgSe
2.CB.05Rudashevskyite
(Fe,Zn)S
2.CB.10Chalcopyrite
CuFeS
 
2
2.CB.10Eskebornite
CuFeSe
 
2
2.CB.10Gallite
CuGaS
 
2
2.CB.10Haycockite
Cu
 
4
Fe
 
5
S
 
8
2.CB.10Lenaite
AgFeS
 
2
2.CB.10Mooihoekite
Cu
 
9
Fe
 
9
S
 
16
2.CB.10Putoranite
Cu
 
9
Fe
 
9
S
 
16
2.CB.10Roquesite
CuInS
 
2
2.CB.10Talnakhite
Cu
 
9
(Fe,Ni)
 
8
S
 
16
2.CB.15Černýite
Cu
 
2
(Cd,Zn,Fe)SnS
 
4
2.CB.15Ferrokësterite
Cu
 
2
(Fe,Zn)SnS
 
4
2.CB.15Hocartite
Ag
 
2
(Fe
2+
 
,Zn)SnS
 
4
2.CB.15Idaite
Cu
 
5
FeS
 
6
2.CB.15Kësterite
Cu
 
2
(Zn,Fe)SnS
 
4
2.CB.15Kuramite
Cu
 
3
SnS
 
4
2.CB.15Mohite
Cu
 
2
SnS
 
3
2.CB.15Pirquitasite
Ag
 
2
ZnSnS
 
4
2.CB.15Stannite
Cu
 
2
(Fe,Zn)SnS
 
4
2.CB.15Stannoidite
Cu
+
6
Cu
2+
2
(Fe
2+
 
,Zn)
 
3
Sn
 
2
S
 
12
2.CB.15Velikite
(Cu,Hg)
 
11
Sn
 
4
S
 
16
2.CB.20Chatkalite
Cu
 
6
FeSn
 
2
S
 
8
2.CB.20Mawsonite
Cu
 
6
Fe
 
2
SnS
 
8
2.CB.30Colusite
Cu
 
26
V
 
2
(As,Sn,Sb)
 
6
S
 
32
2.CB.30Germanite
Cu
 
13
Fe
 
2
Ge
 
2
S
 
16
2.CB.30Germanocolusite
Cu
 
26
V
 
2
(Ge,As)
 
6
S
 
32
2.CB.30Nekrasovite
Cu
 
26
V
 
2
(Sn,As,Sb)
 
6
S
 
32
2.CB.30Stibiocolusite
Cu
 
13
V
 
4
(Sb,Sn,As)
 
3
S
 
16
2.CB.30Ovamboite
Cu
 
20
(Fe,Cu,Zn)
 
6
W
 
2
Ge
 
6
S
 
32
2.CB.30Maikainite
Cu
 
20
(Fe,Cu)
 
6
Mo
 
2
Ge
 
6
S
 
32
2.CB.35Hemusite
Cu
 
6
SnMoS
 
8
2.CB.35Kiddcreekite
Cu
 
6
SnWS
 
8
2.CB.35Polkovicite
(Fe,Pb)
 
3
(Ge,Fe)
 
1-x
S
 
4
2.CB.35Renierite
(Cu,Zn)
 
11
(Ge,As)
 
2
Fe
 
4
S
 
16
2.CB.35Vinciennite
Cu
+
7
Cu
2+
3
Fe
2+
2
Fe
3+
2
Sn(As,Sb)S
 
16
2.CB.35Morozeviczite
(Pb,Fe)
 
3
Ge
 
1-x
S
 
4
2.CB.35Catamarcaite
Cu
 
6
GeWS
 
8
2.CB.40Lautite
CuAsS
2.CB.45Cadmoselite
CdSe
2.CB.45Greenockite
CdS
2.CB.45Hypercinnabar
HgS
2.CB.45Wurtzite
(Zn,Fe)S
2.CB.45Rambergite
MnS
2.CB.55Cubanite
CuFe
 
2
S
 
3
2.CB.55Isocubanite
CuFe
 
2
S
 
3
2.CB.60Picotpaulite
TlFe
 
2
S
 
3
2.CB.60Raguinite
TlFeS
 
2
2.CB.65Argentopyrite
AgFe
 
2
S
 
3
2.CB.65Sternbergite
AgFe
 
2
S
 
3
2.CB.70Sulvanite
Cu
 
3
VS
 
4
2.CB.75Vulcanite
CuTe
2.CB.80Empressite
AgTe
2.CB.85Muthmannite
(Ag,Au)Te

Other Names for Laforêtite

Synonyms:
IMA1995-006
German names:
Laforêtit
Russian names:
Лафоретит
Spanish names:
Laforêtita

Other Information

Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Laforêtite

Reference List:Meisser, N., Thelin, P., Chiappero, P.J., and Maurel, C. (1999) Laforêtite, AgInS2, a new mineral of the chalcopyrite group from the Montgros mine, Haute-Loire, France. European Journal of Mineralogy (1999): 11: 891-897.

Mineralogical Record: 31: 368.

Internet Links for Laforêtite

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  • Raman and XRD data at RRUFF project
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  • Laforêtite details from Handbook of Mineralogy (PDF)
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    Localities for Laforêtite

    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    France
     
    • Auvergne
      • Haute-Loire
        • Pinols
          • Pinols
    		Meisser N. et al (1999) European Journal of Mineralogy 11: 891-897.
    Japan
     
    • Hokkaido Island
      • Sapporo
    Mineral and/or Locality
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