Langite

General Information:
 Chemical Formula:
Cu4(SO4)(OH)6·2(H2O)
 Composition:
(Molecular Weight = 372.75 gm)
Copper 51.14 % Cu
Hydrogen 1.62 % H 
Sulfur 8.60 % S 
Oxygen 38.63 % O 
 Empirical Formula:
Cu3(SO4)(OH)4·(H2O)
 Name Origin:
Named after the Viennese physicist, V. von Lang (1838-1921).
Physical Properties:
 Cleavage:
[001] Perfect, [010] Distinct
 Color:
blue green, green blue, or sky blue.
 Density:
3.5
 Diaphaniety:
Translucent
 Habits:
Concretionary - Rounded massive fine-grained materials., Fibrous - Crystals made up of fibers., Earthy - Dull, clay-like texture with no visible crystalline affinities, (e.g. howlite) .
 Hardness:
2.5-3 - Finger Nail-Calcite
 Luster:
Vitreous (Glassy)
 Streak:
greenish blue
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