Macfallite

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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