Trigonal
Pyrargyrite — “dark ruby silver” — is the antimony analogue of proustite. The pair forms the classic “ruby silver” sulfosalts of historic silver mining: pyrargyrite is the more abundant, deeper-red and slightly more stable to light exposure.
Occurrence
Type locality: St. Andreasberg (Harz, Germany). Other historic sources: Freiberg (Germany), Příbram (Czech Rep.), Hiendelaencina (Spain), Guanajuato (Mexico). Chinese occurrences are minor.
Identification
Nearly black-red translucent trigonal prisms + adamantine luster + purplish-red streak. Pyrargyrite is darker than proustite (which is brighter scarlet) and slightly more stable to light. The streak color difference is decisive — proustite’s is brick-red, pyrargyrite’s is purplish.
Collector Notes
Příbram and Freiberg pyrargyrite specimens with sharp scalenohedral crystals are historical classics. Light-sensitive but slightly less so than proustite.