Mineral phase
IMA name
Vermiculite
Type
Class
silicate mineral
Compound type
phyllosilicate
Chemical composition
Formula
$(Mg,Fe^{2+},Al)_3(Al,Si)_4O_{10}(OH)_2\bullet 4(H_2O)$
Chemical formula
(Mg,Fe2+,Al)3(Al,Si)4O10(OH)2•4(H2O)
Elemental formula
(Al)0-7 (Mg)0-3 (Fe2+)0-3 (Si)0-4 O16 H10
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Al$ Aluminium element 0 - 7 constituent element main
$Mg$ Magnesium element 0 - 3 constituent element main
$Fe^{2+}$ Iron(II) cation element 0 - 3 constituent element main
$Si$ Silicon element 0 - 4 constituent element main
$O$ Oxygen element 16 constituent element main
$H$ Hydrogen element 10 constituent element main
Composition comments
Strong variation of Si and Al proportion. Common impurities: Na, K, Ca
Chemical functions
  Function Number
$(OH)^-$ 2
Chemical bonds
  Bond Number
$O^--H$ 1
Oxides
Formula $Al_{2}O_{3}$ $FeO$ $MgO$ $SiO_{2}$ $H_{2}O$
Mass fraction (%)

Strunz

Class
silicates (09)
Division
phyllosilicate (09.E)
Family
with mica sheets, composed of tetrahedral and octahedral nets (09.EC)
Code
09.EC.50

Dana

Major class
silicates (VIII)
Class
phyllosilicate sheets of six-membered rings (71)
Type
with 2:1 layers (71.02)
Group
Mica group (Hydromica subgroup) (71.02.02d)
Code
71.02.02d.03
Phase type
crystalline
Crystal system
monoclinic
Crystal class
prismatic
Crystal class symbol
2/m (C2h)
Crystal spacegroup
C2/m
Molar mass
504.19 $g/mol$
Density
2.3-2.7 $g/cm^3$
State NTP
solid
Refringence type
biaxial
Refringence sign
negative
Birefringence
0.0200
Refraction index $n_{\alpha}$
1.525-1.561
Refraction index $n_{\beta}$
1.545-1.581
Refraction index $n_{\gamma}$
1.545-1.581
Dispersion V
weak, r > v
Pure color
colorless
Color
Colorless, Green, Gray white, Yellow brown, Brown, Yellow
Diaphaneity
translucent
Luster
vitreous
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