Constituent
Name
olivine
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
heterogeneous in multi-phases
Abundance comments
modal abundance computed by Mandon et al. 2021: ~ 2 vol%
Chemical composition
Formula
$(Fe^{2+}_x,Mg_{1-x})_2.SiO_4 \ \ \ \ \ $ where $x=0-1$
Chemical formula
(Fe2+,Mg)2SiO4
Elemental formula
(Fe2+)0-2 (Mg)0-2 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 - 2 constituent element main
$Mg$ Magnesium element 0 - 2 constituent element main
$Si$ Silicon element 1 constituent element main
$O$ Oxygen element 4 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
Oxides comments
FeO de 0 à 70.5%, MgO de 0 à 57.3%, SiO2 de 29.5 à 42.7%

Strunz

Class
silicates (09)
Division
nesosilicate (09.A)
Family
Nesosilicates 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