Mineral phase
IMA name
Glauconite
Type
Class
silicate mineral
Compound type
phyllosilicate
Chemical composition
Formula
$(K,Na)(Fe^{3+},Al,Mg)_2(Si,Al)_4O_{10}(OH)_2$
Chemical formula
(K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2
Elemental formula
(K)0-1 (Na)0-1 (Mg)0-2 (Al)0-2 (Fe3+)0-2 (Si)3-4 O10 H2 (O-)2
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$K$ Potassium element 0 - 1 constituent element main
$Na$ Sodium element 0 - 1 constituent element main
$Mg$ Magnesium element 0 - 2 constituent element main
$Al$ Aluminium element 0 - 2 constituent element main
$Fe^{3+}$ Iron(III) cation element 0 - 2 constituent element main
$Si$ Silicon element 3 - 4 constituent element main
$O$ Oxygen element 10 constituent element main
$(OH)^-$ Hydroxide anion chemical function 2 anionic radical main
Composition comments
Common Impurities: Fe^{2+}, Ti, Ca, P
Chemical functions
  Function Number
$(OH)^-$ 2
$((Si_2O_5)^{2-})_n$ 2
Chemical bonds
  Bond Number
$O^--H$ 1
$\geq Si-O-$ 6
$\geq Si-O^-$ 2
Oxides
Formula $K_{2}O$ $Na_{2}O$ $MgO$ $Al_{2}O_{3}$ $FeO$ $Fe_{2}O_{3}$ $SiO_{2}$ $H_{2}O$
Mass fraction (%) 6.62 0.36 3.78 3.58 24.31 3.37 53.48 4.22

Strunz

Class
silicates (09)
Division
phyllosilicate (09.E)
Family
with mica sheets, composed of tetrahedral and octahedral nets (09.EC)
Code
09.EC.15

Dana

Major class
silicates (VIII)
Class
phyllosilicate sheets of six-membered rings (71)
Type
with 2:1 layers (71.02)
Group
Mica group (Muscovite subgroup) (71.02.02a)
Code
71.02.02a.05
Phase type
crystalline
Crystal system
monoclinic
Crystal class
prismatic
Crystal class symbol
2/m (C2h)
Crystal spacegroup
C2/m
Molar mass
426.93 $g/mol$
Density
2.4 - 2.95 $g/cm^3$
State NTP
solid
Refringence type
biaxial
Refringence sign
negative
Birefringence
0.0200 - 0.0320
Refraction index $n_{\alpha}$
1.59 - 1.612
Refraction index $n_{\beta}$
1.609 - 1.643
Refraction index $n_{\gamma}$
1.61 - 1.644
Dispersion V
r > v
Color
blue green, green, yellow green
Diaphaneity
translucent to opaque
Luster
earthy
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