gabrielite

{{infobox mineral | name = Gabrielite | category = Sulfide mineral | image = Gabrielite.jpg | caption = A small gabrielite crystal | formula = | IMAsymbol = Gab | molweight = | strunz = 2.HD.60 | system = Triclinic | class = Pinacoidal () (same H-M symbol) | symmetry = P | unit cell = a = 12.138, b = 12.196 c = 15.944 [Å]; α = 78.537° β = 84.715°, γ = 60.47°; Z = 6 | color = Grey to black | habit = Pseudo Hexagonal | twinning = Common, with (100) as twin plane | cleavage = Perfect on {001} | fracture = uneven | tenacity = | mohs = 1.5 - 2 | luster = Metallic | refractive = | opticalprop = | birefringence = weak 470nm R=30.53%546nm R=29.1%589nm R=27.94%650nm R=26.35% | pleochroism = | streak = Blackish red | gravity = | density = 5.38 g/cm3 | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Opaque | other = | references = }} Gabrielite is an extremely rare thallium sulfosalt mineral with a chemical formula of or .

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. 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.