Wiktionary
gabrielite
n. (context mineral English) A triclinic-pinacoidal black mineral containing antimony, arsenic, copper, silver, sulfur, and thallium.
Wikipedia
Gabrielite
Gabrielite is a rare thallium sulfosalt mineral with a chemical formula of TlAgCu(As,Sb)S or TlAgCuAsS.
It was first reported in 2002 for its occurrence in the Lengenbach quarry, Binntal, Valais, Switzerland, and 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.