Tetradymite
Mineral Bi2Te2S
About it
Soft, pale steel-grey plates that peel into flexible flakes, found with gold in quartz veins and skarns. Its name means fourfold, after its twinned crystals.
- Type
- Mineral
- Group
- Telluride, tetradymite group
- Formula
- Bi2Te2S
- Hardness (Mohs)
- 1.5–2
- Specific gravity
- 7.1–7.7
- Streak
- steel grey
- Lustre
- metallic
- Crystal system
- Trigonal
- Colours
- pale steel grey, dull to iridescent tarnish
- Transparency
- opaque
- Cleavage and fracture
- perfect basal, flexible plates
Typical values: real specimens vary. For more, see mindat.org.