Franckeite
Mineral Fe(Pb,Sn)6Sn2Sb2S14
Take care.
- Contains lead: Wash your hands after handling it, keep it away from children, and don't make dust.
- Toxic: Wash your hands after handling it, don't lick or taste it, and don't make dust.
About it
Blackish grey flexible foils and rosettes of lead-tin-antimony sulfide. Named for the mining engineers Carl and Ernest Francke; best known from Bolivian tin mines.
- Type
- Mineral
- Group
- Sulfosalt
- Formula
- Fe(Pb,Sn)6Sn2Sb2S14
- Hardness (Mohs)
- 2.5–3
- Specific gravity
- 5.8–6
- Streak
- greyish black
- Lustre
- metallic
- Crystal system
- Triclinic
- Colours
- blackish grey
- Transparency
- opaque
- Cleavage and fracture
- perfect in one direction, flexible foils
Typical values: real specimens vary. For more, see mindat.org.