Sternbergite
Mineral AgFe2S3
About it
Very soft, flexible brownish plates of silver-iron sulfide, often in rosettes, that tarnish blue. Known from Jáchymov, Czechia, and Freiberg, Germany; named for Kaspar Sternberg.
- Type
- Mineral
- Group
- Sulfide
- Formula
- AgFe2S3
- Hardness (Mohs)
- 1–1.5
- Specific gravity
- 4.1–4.3
- Streak
- black
- Lustre
- metallic
- Crystal system
- Orthorhombic
- Colours
- pinchbeck brown, violet-blue tarnish
- Transparency
- opaque
- Cleavage and fracture
- perfect basal, flexible thin plates
Typical values: real specimens vary. For more, see mindat.org.