General Information:
Chemical Formula:
(Mn++,Mg,Zn,Fe++)3(Si,As)2O510(OH,Cl)4
Environment:
Forms as an alteration product of primary manganese silicates such as rhodonite.
IMA Status:
Approved IMA 1963
Locality:
Harstig mine, Pajsberg, Varmland, Sweden.
Name Origin:
Named from the Greek for "nut" and "felt," in allusion to its brown color and felted structure.
Physical Properties:
Cleavage:
[001] Good
Color:
reddish brown, yellow, greenish brown, or orange brown.
Density:
2.87
Habits:
Pseudo Hexagonal - Crystals show a hexagonal outline., Platy - Sheet forms (e.g. micas)., Massive - Uniformly indistinguishable crystals forming large masses.
Hardness:
3-3.5 - Calcite-Copper Penny
Streak:
light brown
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