General Information:
Chemical Formula:
Ca2MgAl2(SiO4)(Si2O7)(OH)2·(H2O)
Composition:
(Molecular Weight = 470.70 gm)
Calcium 17.03 % Ca
Magnesium 5.16 % Mg
Aluminum 11.46 % Al
Silicon 17.90 % Si
Hydrogen 0.86 % H
Oxygen 47.59 % O
Empirical Formula:
Ca2MgAl2(SiO4)(Si2O7)(OH)2·(H2O)
Environment:
Meta-basalt or gabbroic rocks.
IMA Status:
Approved IMA 1973
Locality:
Calumet mine, Houghton County, Keweenaw Peninisula, Michigan, USA.
Name Origin:
Named after the American geologist, R. Pumpelly (1837-1923).
Physical Properties:
Cleavage:
[001] Good, [100] Good
Color:
blue green, olive green, or brown.
Density:
3.2
Diaphaniety:
Translucent
Habits:
Spherical - Spherical, rounded aggregates., Fibrous - Crystals made up of fibers., Massive - Lamellar - Distinctly foliated fine-grained forms.
Hardness:
5.5 - Knife Blade
Luminescence:
None.
Luster:
Vitreous (Glassy)
Streak:
white
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