General Information:
Chemical Formula:
Ca2(Mn+++,Al)3(SiO4)(Si2O7)(OH)3
Composition:
(Molecular Weight = 542.26 gm)
Calcium 14.78 % Ca
Manganese 25.33 % Mn
Aluminum 2.49 % Al
Silicon 15.54 % Si
Hydrogen 0.56 % H
Oxygen 41.31 % O
Empirical Formula:
Ca2Mn3+2.5Al0.5(SiO4)(Si2O7)(OH)3
Environment:
Associated with other Mn-silicates.
IMA Status:
Approved IMA 1979
Locality:
Manganese Lake, Copper Harbor, Keweenaw County, Michigan, USA.
Name Origin:
Named for Russell P. MacFall, a dedicated amateur mineralogist.
Physical Properties:
Cleavage:
[001] Perfect
Color:
brown, maroon, reddish brown, or pink.
Density:
3.43
Habits:
Acicular - Occurs as needle-like crystals., Aggregates - Made of numerous individual crystals or clusters., Twinning Common - Crystals are usually twinned.
Hardness:
5-5.5 - Apatite-Knife Blade
Luster:
Vitreous - Silky
Streak:
brown
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