Mineral - Augite
Augite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
(Ca,Fe)(Mg,Fe,Ti)[Si₂O₆]
Unit Cell
a=9.70 b=8.84 c=5.27 β=107° Z=4
Physical Properties
Hardness
5.5 - 6
Streak
blackbrowngraygreengreen blackgreen grey
Density
Normal (2-3,5)
Cleavage
Perfect after {110}, shows 90° cleavage angle to {100}
Fracture
uneven
Tenacity
Brittle
Optical Properties
Color
blackbrowngreen
Birefringence
0.026 - 0.039
Luster
Vitreous,
Resinous
Transparency
translucent,
opaque
Pleochroism
X: Grün-Gelb-Braun
Y: Braun-Gelb-Violett
Z: Grau-Grün-Violett
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
C2/c (15)
Habit
blocky, granular, prismatic, tabular
Formation
In many igneous rocks
Through metamorphism
Paragenesis
Twinning
Contact twins after {100}, cross-shaped penetration twins at a 90° or 60° angle
Rarity
Very common
Synonyms
Augite
Composition
Elements
Mass
SiO₂
51.83
TiO₂
0.49
Al₂O₃
3.07
Fe₂O₃
1.38
FeO
7.21
MnO
0.17
MgO
16.00
CaO
19.21
Na₂O
0.27
K₂O
0.02
H₂O
0.58
USA (Dana 1892)
Groups and Members
Pyroxene-Group
Clinopyroxene-Subgroup
Name and first discovery : Named after the ancient Greek word "auge" for "shine", in reference to the striking mother-of-pearl shine on the cleavage surfaces.
Chemistry :
Synonyms : basaltine, violetite, volcanite
Varieties : Asteroite, Fassaite, Ferroaugite, Jeffersonite, Sodium Augite, Titanium Augite
Abbreviation : Aug
literature
Dana, J. D., & Dana, E. S. (1892). The system of mineralogy of James Dwight Dana, 1837-1868: descriptive mineralogy . J. Wiley & sons.