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
Constituent abundance in material
Relevance
main - major
Arrangement
single phase
Mass fraction
1.0 $\pm$ 0.001
Chemical composition
Formula
$(Ca_{0.64},Fe^{2+}_{0.34},Mg_{1.02})Si_2O_6$
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
$Fe^{2+}$ Iron(II) cation element 0.34 - 1.5 1.0 constituent element main
$Fe^{3+}$ 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, $Fe^{3+}$, Ti (also disordered) - Common impurities: Cr, Mn, Zn, K - from "Electron microprobe analysis shows that Pyroxenes lie in the Augite field ($Ca_{32}Mg_{51}Fe_{17}$)"; Allen et al. 1998 - Assume no Na, $Fe^{3+}$, Ti and Al replacement
Oxides
Formula $CaO$ $Na_{2}O$ $MgO$ $FeO$ $Fe_{2}O_{3}$ $TiO_{2}$ $Al_{2}O_{3}$ $SiO_{2}$
Mass fraction (%) 16.2 11.0 18.6 54.2
Oxides comments
For $(Ca_0.9,Mg_{0.9},Fe^{2+}_{0.2}).(Si_{1.6},Al_{0.4})_2O_6$ - 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 $g/cm^3$
Refringence type
biaxial
Refringence sign
positive
Birefringence
0.026
Refraction index $n_{\alpha}$
1.680 - 1.735
Refraction index $n_{\beta}$
1.684 - 1.741
Refraction index $n_{\gamma}$
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