Constituent
Name
Olivine Fa28
IMA name
Fayalite-Forsterite series
Class
silicate mineral
Compound type
nesosilicate
Comments
Equivalent Space Group: Pbnm (62)
Constituent abundance in material
Relevance
main - major
Arrangement
homogeneous in multi-phases
Mass fraction
0.562 $\pm$ 0.005
Chemical composition
Formula
$(Fe^{2+}_{0.28},Mg_{0.72})_2.SiO_4 $
Chemical formula
(Fe2+)0.56(Mg)1.44SiO4
Elemental formula
(Fe2+)0.56 Mg1.44 Si O4
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Fe^{2+}$ Iron(II) cation element 0.56 1.0 constituent element main
$Mg$ Magnesium element 1.44 1.0 constituent element main
$Si$ Silicon element 1 1.0 constituent element main
$O$ Oxygen element 4 1.0 constituent element main
Composition comments
perfect solid solution - Common impurities: Mn, Ni
Chemical functions
  Function Number
$(SiO_4)^{4-}$ 1
Chemical bonds
  Bond Number
$\geq Si-O^-$ 4

Strunz

Class
silicates (09)
Division
nesosilicate (09.A)
Family
without additional anions; cations in octahedral [6] coordination (09.AC)
Code
09.AC.05

Dana

Major class
silicates (VIII)
Class
nesosilicate insular SiO4 groups only (51)
Type
with all cations in octahedral [6] coordination (51.03)
Group
Olivine group (51.03.01)
Code
51.03.01.00
Phase type
crystalline
Crystal system
orthorhombic
Crystal class
dipyramidal
Crystal class symbol
mmm (D2h)
Crystal spacegroup
Pnma
Molar mass
140.69 - 203.78 $g/mol$
Density
3.21 - 4.39 $g/cm^3$
Refringence type
biaxial
Refringence sign
negative
Birefringence
0.0330 - 0.0510
Refraction index $n_{\alpha}$
1.636 - 1.824
Refraction index $n_{\beta}$
1.65 - 1.864
Refraction index $n_{\gamma}$
1.669 - 1.875
Color
colorless, brown, green, yellow, yellow green, white, black
Diaphaneity
transparent to translucent
Luster
vitreous