Definition of Aegirine-augite

Aegirine-augite

General Information:
 Chemical Formula:
(Ca,Na)(Mg,Fe++,Fe+++)[Si2O6]
 Composition:
(Molecular Weight = 228.05 gm)
Sodium 2.52 % Na
Calcium 13.18 % Ca
Magnesium 5.33 % Mg
Iron 12.24 % Fe
Silicon 24.63 % Si
Oxygen 42.09 % O 
 Empirical Formula:
Ca0.75Na0.25Mg0.5Fe2+0.25Fe3+0.25(Si2O6)
 Environment:
Characteristic mineral of alkaline rocks, particularly syenites and iron-rich metamorphic and metasomatic rocks.
 IMA Status:
Not IMA Approved
 Locality:
Common world-wide.
 Name Origin:
Name derived from its intermediate pyroxene composition. This is not an end-member species.
Physical Properties:
 Cleavage:
[110] Very Good, [100] Parting
 Color:
dark green, black, green, pale greenish yellow, or greenish gray.
 Density:
3.4 - 3.6, Average = 3.5
 Diaphaniety:
Translucent to opaque
 Habits:
Fibrous - Crystals made up of fibers., Anhedral Grains - Granular minerals without the expression of crystal shapes, Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
 Hardness:
6 - Orthoclase
 Luster:
Vitreous (Glassy)
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