General Information:
Chemical Formula:
Na2Ca(Mg,Fe++)4Fe+++Si7AlO22(OH)2
Composition:
(Molecular Weight = 824.40 gm)
Sodium 5.58 % Na
Calcium 4.86 % Ca
Magnesium 8.84 % Mg
Aluminum 3.27 % Al
Iron 6.77 % Fe
Silicon 23.85 % Si
Hydrogen 0.24 % H
Oxygen 46.58 % O
Empirical Formula:
Na2CaMg3Fe2+Si7AlO22(OH)2
Environment:
Found in basic alkaline igneous rocks.
IMA Status:
Approved IMA 1997
Name Origin:
Named for its composition and from the Greek for "carrying down", in allusion to its volcanic origin.
Physical Properties:
Cleavage:
[110] Good, [010] Parting
Color:
dark green.
Density:
3.2 - 3.5, Average = 3.35
Diaphaniety:
Translucent
Hardness:
5-6 - Between Apatite and Orthoclase
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