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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.


Chalcopyrite Group.

Classification of Laforêtite

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

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
Analytical 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

Member of Group:
Chalcopyrite Group:
ABX
 
2
Related Minerals - Nickel-Strunz Grouping):

- +
2.CB.05aColoradoite
HgTe
2.CB.05aHawleyite
CdS
2.CB.05aMetacinnabar
HgS
2.CB.05cPolhemusite
(Zn,Hg)S
2.CB.05bSakuraiite
(Cu,Zn,Fe)
 
3
(In,Sn)S
 
4
2.CB.05aSphalerite
(Zn,Fe
2+
 
)S
2.CB.05aStilleite
ZnSe
2.CB.05aTiemannite
HgSe
2.CB.05UM1998-15-S:CuFeZn
Cu
 
2
Fe
 
3
Zn
 
5
S
 
10
2.CB.05aRudashevskyite
(Fe,Zn)S
2.CB.10aChalcopyrite
CuFeS
 
2
2.CB.10aEskebornite
CuFeSe
 
2
2.CB.10aGallite
CuGaS
 
2
2.CB.10bHaycockite
Cu
 
4
Fe
 
5
S
 
8
2.CB.10aLenaite
AgFeS
 
2
2.CB.10bMooihoekite
Cu
 
9
Fe
 
9
S
 
16
2.CB.10bPutoranite
Cu
 
9
(Fe,Ni)
 
9
S
 
16
2.CB.10aRoquesite
CuInS
 
2
2.CB.10bTalnakhite
Cu
 
9
(Fe,Ni)
 
8
S
 
16
2.CB.15aČernýite
Cu
 
2
(Cd,Zn,Fe)SnS
 
4
2.CB.15aFerrokësterite
Cu
 
2
(Fe,Zn)SnS
 
4
2.CB.15aHocartite
Ag
 
2
(Fe
2+
 
,Zn)SnS
 
4
2.CB.15aIdaite
Cu
 
5
FeS
 
6
2.CB.15aKësterite
Cu
 
2
(Zn,Fe)SnS
 
4
2.CB.15aKuramite
Cu
 
3
SnS
 
4
2.CB.15bMohite
Cu
 
2
SnS
 
3
2.CB.15aPirquitasite
Ag
 
2
ZnSnS
 
4
2.CB.15aStannite
Cu
 
2
(Fe,Zn)SnS
 
4
2.CB.15cStannoidite
Cu
+
6
Cu
2+
2
(Fe
2+
 
,Zn)
 
3
Sn
 
2
S
 
12
2.CB.15aVelikite
(Cu,Hg)
 
11
Sn
 
4
S
 
16
2.CB.15cUM2006-11-S:CuFeGeZn
Cu
 
8
(Fe,Zn)
 
3
Ge
 
2
S
 
12
 (?)
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.35aHemusite
Cu
 
6
SnMoS
 
8
2.CB.35aKiddcreekite
Cu
 
6
SnWS
 
8
2.CB.35aPolkovicite
(Fe,Pb)
 
3
(Ge,Fe)
 
1-x
S
 
4
2.CB.35aRenierite
(Cu,Zn)
 
11
(Ge,As)
 
2
Fe
 
4
S
 
16
2.CB.35aVinciennite
Cu
+
7
Cu
2+
3
Fe
2+
2
Fe
3+
2
Sn(As,Sb)S
 
16
2.CB.35aMorozeviczite
(Pb,Fe)
 
3
Ge
 
1-x
S
 
4
2.CB.35bCatamarcaite
Cu
 
6
GeWS
 
8
2.CB.40Lautite
CuAsS
2.CB.45Cadmoselite
CdSe
2.CB.45Greenockite
CdS
2.CB.45Wurtzite
(Zn,Fe)S
2.CB.45Rambergite
MnS
2.CB.55aCubanite
CuFe
 
2
S
 
3
2.CB.55bIsocubanite
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
AuAgTe
 
2

Other Names for Laforêtite

Synonyms:
IMA1995-006
Other Languages:
German:Laforêtit
Russian:Лафоретит
Spanish: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
  • American Mineralogist Crystal Structure Database
  • Search for Laforêtite in the Natural History Museum (London) online catalogue
  • 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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