General Information:
Chemical Formula:Ca2(Mn+++,Al)3(SiO4)(Si2O7)(OH)3
Composition:(Molecular Weight = 542.26 gm)Calcium 14.78 %
CaManganese 25.33 %
MnAluminum 2.49 %
AlSilicon 15.54 %
SiHydrogen 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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