Mineral phase
IMA name
Forsterite
Class
silicate mineral
Compound type
nesosilicate
Comments
Forsterite: name by extension of (Fe,Mg)2SiO4 in the range Fe=0-10% - Equivalent Space Group: Pbnm (62)
Formula
$Mg_2.SiO_4$
Chemical formula
Mg2SiO4
Elemental formula
Mg2 Si O4
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Mg$ Magnesium element 2 constituent element main
$Si$ Silicon element 1 constituent element main
$O$ Oxygen element 4 constituent element main
Composition comments
Common substitution: Fe
Chemical functions
  Function Number
$(SiO_4)^{4-}$ 1
Chemical bonds
  Bond Number
$\geq Si-O^-$ 4
Oxides
Formula $MgO$ $SiO_{2}$
Mass fraction (%) 57.29 42.71

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
51.03.01.02
Phase type
crystalline
Crystal system
orthorhombic
Crystal class
dipyramidal
Crystal class symbol
mmm (D2h)
Crystal spacegroup
Pnma
Composition order
ordered
Molar mass
140.69 $g/mol$
Density
3.271 $g/cm^3$
State NTP
solid
Refringence type
biaxial
Refringence sign
negative
Birefringence
0.0330
Refraction index $n_{\alpha}$
1.636
Refraction index $n_{\beta}$
1.650
Refraction index $n_{\gamma}$
1.669
Dispersion V
r > v or r < v
Pure color
green
Color
green, yellow, yellow green, white
Diaphaneity
transparent to translucent
Luster
vitreous