General Information:
Chemical Formula:
(K,Na)3(Fe++,Mn)6(Nb,Ti)2[Si8O24](O,OH,F)7
Composition:
(Molecular Weight = 1,345.90 gm)
Potassium 7.26 % K
Sodium 0.85 % Na
Titanium 0.71 % Ti
Manganese 4.08 % Mn
Niobium 12.43 % Nb
Iron 20.75 % Fe
Silicon 16.69 % Si
Hydrogen 0.15 % H
Oxygen 35.66 % O
Fluorine 1.41 % F
Empirical Formula:
K2.5Na0.5Fe2+5Mn2+Nb1.8Ti0.2Si8O28OH2F
Environment:
Flakes in an albite-arfvedsonite paragneiss.
IMA Status:
Approved IMA 1964
Locality:
Ten Mile Lake, Seal Lake area, Labrador, NF, Canada.
Name Origin:
Named for the niobium content and foliated character common to the astrophyllite group.
Physical Properties:
Cleavage:
[001] Perfect
Color:
brown.
Density:
3.42
Diaphaniety:
Translucent to Opaque
Habits:
Foliated - Two dimensional platy forms., Flakes - Flat, thin crystals or aggregates.,
Hardness:
3-4 - Calcite-Fluorite
Luster:
Vitreous - Adamantine
More details...