Franckeite
A variety of Franckeite Group
What is Franckeite?
Franckeite, chemical formula Pb5Sn3Sb2S14, belongs to a family of complex sulfide minerals. Franckeite is a sulfosalt. It is closely related to cylindrite. It was first described in 1893 for an occurrence in Chocaya, Potosí Department, Bolivia. It is named after the mining engineers, Carl and Ernest Francke. It can be found in Bolivia at Poopó in Oruro and at Las Aminas, southeast of Chocaya, in Potosi. Franckeite has an average density of 5.7 and can be both grayish black, blackish gray in color. It occurs in hydrothermal silver-tin deposits in Bolivia and in contact metamorphosed limestone deposit in the Kalkar quarry in California. It occurs with cylindrite, teallite, plagionite, zinkenite, cassiterite, wurtzite, pyrrhotite, marcasite, arsenopyrite, galena, pyrite, sphalerite, siderite and stannite.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Franckeite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Franckeite Localities Map
See where Franckeite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
More Images
Quick Facts
Physical Properties
- Color
- Grey-black, black; iridescent at times
- Hardness (Mohs)
- 2.5 - 3
- Density
- 5.88 g/cm³
- Streak
- Grayish black
Chemical Properties
- Chemical Formula
- Fe2+(Pb,Sn2+)6Sn4+2Sb2S14
- Elements
- Fe, Pb, S, Sb, Sn
Also Known As
Identify Franckeite Instantly
- Snap a photo, get instant results
- 6,700+ rocks, minerals & crystals
- Discover collecting spots near you
Franckeite FAQs
How do I identify Franckeite?
Franckeite can be identified by its hardness of 2.5 - 3 on the Mohs scale, Grey-black color. Look for these key characteristics when examining specimens.
What color is Franckeite?
Franckeite typically appears in Grey-black, black; iridescent at times. Color can vary depending on impurities and formation conditions.
How hard is Franckeite?
Franckeite has a hardness of 2.5 - 3 on the Mohs scale. This makes it a soft mineral that can be scratched easily.