Mineral phase
IMA name
Berthierine
Type
Class
silicate mineral
Compound type
phyllosilicate
Comments
1M polytype. Exist another polytype: 1H
Chemical composition
Formula
$(Fe^{2+},Fe^{3+},Al,Mg)_(2-3)(Si,Al)_2O_5(OH)_4$
Chemical formula
(Fe2+,Fe3+,Al,Mg)2-3((Si,Al)2O5)(OH)4
Elemental formula
(Mg)0-1 (Fe2+)1-2 (Fe3+)0-1 (Al)0-2 (Si)1-2 O9 H4
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Mg$ Magnesium element 0 - 1 constituent element main
$Fe^{2+}$ Iron(II) cation element 1 - 2 constituent element main
$Fe^{3+}$ Iron(III) cation element 0 - 1 constituent element main
$Al$ Aluminium element 0 - 2 constituent element main
$Si$ Silicon element 1 - 2 constituent element main
$O$ Oxygen element 9 constituent element main
$H$ Hydrogen element 4 constituent element main
Composition comments
Common impurities: Ti, Ca, Mn
Chemical functions
  Function Number
$(OH)^-$ 4
Chemical bonds
  Bond Number
$O^--H$ 1
Oxides
Formula $MgO$ $Al_{2}O_{3}$ $FeO$ $Fe_{2}O_{3}$ $SiO_{2}$ $H_{2}O$
Mass fraction (%) 2.44 29.28 32.58 4.83 19.98 10.89
Oxides comments
$(Fe^{2+}_{1.5},Fe^{3+}_{0.2},Al,Mg_{0.2})(Si_{1.1},Al_{0.9}O_5)(OH)_4$

Strunz

Class
silicates (09)
Division
phyllosilicate (09.E)
Family
Phyllosilicates with kaolinite layers (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 (Amesite subgroup) (71.01.02c)
Code
71.01.02c.02
Phase type
crystalline
Crystal system
monoclinic
Crystal class
domatic
Crystal class symbol
m (Cs)
Crystal spacegroup
Cm
Molar mass
308.6 - 353.1 $g/mol$
Density
2.93 - 3.06 $g/cm^3$
State NTP
solid
Refringence type
biaxial
Refringence sign
unknown
Birefringence
0.030
Refraction index $n_{\alpha}$
1.620
Refraction index $n_{\gamma}$
1.650
Dispersion V
r < v strong
Pure color
green
Color
green yellow, brown green, dark green
Diaphaneity
transparent to translucent
Luster
pearly
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