Deep red trechmannite associated to minoritary realgar and pyrite. From a 1992 find. Analyzed with EDS. From: Lengenbach Quarry, Binntal, Wallis, Switzerland. — Photo: David Hospital · CC BY-SA 4.0
Trechmannite
Trechmannite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula AgAsS₂.
It crystallizes in the hexagonal crystal system (space group R-3).
Key properties: Mohs hardness 1.5–2; specific gravity 4.77; Scarlet- vermilion streak; Adamantine luster; optically uniaxial.
IMA symbol Trh, grandfathered status — known before the IMA’s founding, named in 1905.
Of hydrothermal origin, in dolostone (Binntal, Switzerland).
It is found associated with Seligmannite, tennantite, pyrite, chromian muscovite (Binntal, Switzerland).
The mineral was named to honor Dr. Charles Otto Trechmann (1851–1917), English crystallographer.