| Gabrielite | |
|---|---|
 A small gabrielite crystal | |
| General | |
| Category | Sulfide mineral |
| Formula (repeating unit) | Tl6Ag3Cu6(As,Sb)9S21 |
| IMA symbol | Gab[1] |
| Strunz classification | 2.HD.60 |
| Crystal system | Triclinic |
| Crystal class | Pinacoidal (1) (same H-M symbol) |
| Space group | P1 |
| Unit cell | a = 12.138, b = 12.196 c = 15.944 [Å]; α = 78.537° β = 84.715°, γ = 60.47°; Z = 6 |
| Identification | |
| Color | Grey to black |
| Crystal habit | Pseudo Hexagonal |
| Twinning | Common, with (100) as twin plane |
| Cleavage | Perfect on {001} |
| Fracture | uneven |
| Mohs scale hardness | 1.5 - 2 |
| Luster | Metallic |
| Streak | Blackish red |
| Diaphaneity | Opaque |
| Density | 5.38 g/cm3 |
| Birefringence | weak 470nm R=30.53% 546nm R=29.1% 589nm R=27.94% 650nm R=26.35% |
| References | [2][3] |
Gabrielite is an extremely rare thallium sulfosalt mineral with a chemical formula of Tl6Ag3Cu6(As,Sb)9S21[2] or Tl2AgCu2As3S7.[3]
It was first reported in 2002 for its occurrence in the Lengenbach quarry, Binntal, Valais, Switzerland. According to Faszination Lengenbach (2008), only 2 specimens are known. A few dozen tiny fragments like the one pictured are circulating few collections. Named after Walter Gabriel (born 1943), a Swiss mineral photographer.[2][3] This region was transformed during the greenschist-garnet/amphibolite facies of metamorphism. Due to this many rare sulfosalts like gabrielite are found in this part of Switzerland.
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b c "Gabrielite". Mindat.org. Retrieved 16 September 2010.
- ^ a b c Webmineral data