Constituent
Name
Augite
IMA name
Augite
Class
silicate mineral
Compound type
inosilicate
Comments
generaly crystalline
The full Ca, ordered Orthopyroxene equivalent of Augite is the Diopside-Hedenbergite series
Relevance
main - major
Arrangement
single phase
Mass fraction
1.0 ± 0.001
Formula
(Ca0.64,Fe0.342+,Mg1.02)Si2O6
Chemical formula
(Ca,Mg,Fe2+)2(Si,Al)2O6
Elemental formula
(Ca)0.64-0.9 Na0 (Mg)1.02-1.5 (Fe2+)0.34-1.5 (Fe3+)0 Ti0 Al0 Si2 O6
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
Ca Calcium element 0.64 - 0.9 1.0 constituent element main
Na Sodium element 0 1.0 constituent element replacement
Mg Magnesium element 1.02 - 1.5 1.0 constituent element main
Fe2+ Iron(II) cation element 0.34 - 1.5 1.0 constituent element main
Fe3+ Iron(III) cation element 0 1.0 constituent element replacement
Ti Titanium element 0 1.0 constituent element replacement
Al Aluminium element 0 1.0 constituent element replacement
Si Silicon element 2 1.0 constituent element main
O Oxygen element 6 1.0 constituent element main
Composition comments
relatively low in calcium with some disorder of occupancies of Fe2+ and Mg in both octahedral sites - Common substitution: Na, Al, Fe3+, Ti (also disordered) - Common impurities: Cr, Mn, Zn, K - from "Electron microprobe analysis shows that Pyroxenes lie in the Augite field (Ca32Mg51Fe17)"; Allen et al. 1998 - Assume no Na, Fe3+, Ti and Al replacement
Oxides
Formula CaO Na2O MgO FeO Fe2O3 TiO2 Al2O3 SiO2
Mass fraction (%) 16.2 11.0 18.6 54.2
Oxides comments
For (Ca0.9,Mg0.9,Fe0.22+).(Si1.6,Al0.4)2O6 - calculated with elemental formula

Strunz

Class
silicates (09)
Division
inosilicate (09.D)
Family
with 2-periodic single chains, Si2O6; pyroxene family (09.DA)
Code
09.DA.15

Dana

Major class
silicates (VIII)
Class
inosilicate single-width unbranched chains, w=1 (65)
Type
with chains P=2 (65.01)
Group
C2/c clinopyroxenes (Ca clinopyroxenes) (65.01.03a)
Code
65.01.03a.03
Phase type
crystalline
Crystal system
monoclinic
Crystal class
prismatic
Crystal class symbol
2/m (C2h)
Crystal spacegroup
C2/c
Texture
polycrystalline
Molar mass
221.6 g/mol
Density
3.2 g/cm3
Refringence type
biaxial
Refringence sign
positive
Birefringence
0.026
Refraction index nα
1.680 - 1.735
Refraction index nβ
1.684 - 1.741
Refraction index nγ
1.706 - 1.774
Dispersion V
weak to distinct (r > v)
Color
green, brown green, light brown, purplish brown, dark brown, black
Diaphaneity
translucent to opaque
Luster
vitreous