Proustite
ID: 89
Proustite
Chemical Formula
Ag₃AsS₃
Hardness (Mohs)
2–2.5
Crystal System
Trigonal
Streak
vermilion red
Luster
Adamantine to sub-metallic
Diaphaneity
Transparent to translucent
Color
Scarlet, Vermilion or reddish gray
Crystal Habit / Mode of Occurrence
Prismatic crystals, often well-formed with rhombohedral faces; can also appear as granular or massive aggregates
Fun Facts
Proustite is nicknamed "ruby silver" because of its striking red color and silver content. However, it darkens when exposed to light — so collectors often store it in darkness to preserve its vibrant hue!