Mineral phase
IMA name
Antigorite
Type
Class
silicate mineral
Compound type
phyllosilicate
Chemical composition
Formula
$(Mg_x,Fe^{2+}_{1-x})_3.Si_2O_5(OH)_4 \ \ \ \ \ $ where $x=0-1$
Chemical formula
(Mg,Fe2+)3Si2O5(OH)4
Elemental formula
(Mg)2-3 (Fe2+)0-1 Si2 O9 H4
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Mg$ Magnesium element 2 - 3 constituent element main
$Fe^{2+}$ Iron(II) cation element 0 - 1 constituent element main
$Si$ Silicon element 2 constituent element main
$O$ Oxygen element 9 constituent element main
$H$ Hydrogen element 4 constituent element main
Composition comments
Common impurities: Ni, Al, Mn
Chemical functions
  Function Number
$(OH)^-$ 4
Chemical bonds
  Bond Number
$O^--H$ 1
Oxides
Formula $MgO$ $FeO$ $SiO_{2}$ $H_{2}O$
Mass fraction (%) 30.15 17.92 39.95 11.98

Strunz

Class
silicates (09)
Division
phyllosilicate (09.E)
Family
with kaolinite layers composed of tetrahedral and octahedral nets (09.ED)
Code
09.ED.15

Dana

Major class
silicates (VIII)
Class
phyllosilicate sheets of six-membered rings (71)
Type
with 1:1 layers (71.01)
Group
Serpentine group (-Antigorite- subgroup) (71.01.02a)
Code
71.01.02a.01
Phase type
crystalline
Crystal system
monoclinic
Crystal class
domatic
Crystal class symbol
m (Cs)
Crystal spacegroup
Cm
Molar mass
300.77 $g/mol$
Density
2.5 - 2.6 $g/cm^3$
State NTP
solid
Refringence type
biaxial
Refringence sign
negative
Birefringence
0-005 - 0.006
Refraction index $n_{\alpha}$
1.555 - 1.567
Refraction index $n_{\beta}$
1.560 - 1.573
Refraction index $n_{\gamma}$
1.560 - 1.573
Dispersion V
weak, r > v
Pure color
white
Color
white, green, green-blue, gray, bluish gray, brown, black
Diaphaneity
translucent to opaque
Luster
vitreous
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