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
Phyllosilicates 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
Links