General Information:
Chemical Formula:
Pb5Sn3Sb2S14
Composition:
(Molecular Weight = 2,084.55 gm)
Tin 17.08 % Sn
Antimony 11.68 % Sb
Lead 49.70 % Pb
Sulfur 21.54 % S
Empirical Formula:
Pb5Sn3Sb2S14
Locality:
Found in Bolivia at Poopo in Oruro and at Las Aminas, southeast of Chocaya, in Potosi.
Name Origin:
Named after the mining engineers, C. and E. Francke.
Physical Properties:
Cleavage:
[001] Perfect
Color:
grayish black or blackish gray.
Density:
5.5 - 5.9, Average = 5.7
Diaphaniety:
Opaque
Habits:
Tabular - Form dimensions are thin in one direction., Massive - Fibrous - Distinctly fibrous fine-grained forms., Radial - Crystals radiate from a center without producing stellar for ms (e.g. stibnite)
Hardness:
2.5 - Finger Nail
Luster:
Metallic
Streak:
grayish black
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