Ecdemite

General Information:
 Chemical Formula:
Pb6As+++2O7Cl4
 Composition:
(Molecular Weight = 1,646.85 gm)
Arsenic 9.10 % As
Lead 75.49 % Pb
Chlorine 8.61 % Cl
Oxygen 6.80 % O 
 Empirical Formula:
Pb6As2O7Cl4
 Locality:
Langban and Harstig mines, Varmland, Sweden.
 Name Origin:
Named from the Greek for "unusual", in reference to the composition.
Physical Properties:
 Cleavage:
[001] Perfect
 Color:
green yellow, yellow, or orange.
 Density:
6.9 - 7.1, Average = 7
 Diaphaniety:
Translucent
 Habits:
Massive - Uniformly indistinguishable crystals forming large masses., Encrustations - Forms crust-like aggregates on matrix., Tabular - Form dimensions are thin in one direction.
 Hardness:
2.5 - Finger Nail
 Luminescence:
Non-fluorescent.
 Luster:
Vitreous - Greasy
 Streak:
light yellow
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