Mineral phase
IMA name
Gehlenite
IMA Code
Gh
Type
Class
silicate mineral
Compound type
sorosilicate
Chemical composition
Formula
$Ca_2Al(AlSi)O_7$
Chemical formula
Ca2Al(AlSi)O7
Elemental formula
(Ca2+)2 Al2 Si O3 (O-)4
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Ca^{2+}$ Calcium cation element 2 constituent cation main
$Al$ Aluminium element 2 constituent element main
$Si$ Silicon element 1 constituent element main
$O$ Oxygen element 3 constituent element main
$O^-$ Oxide anion element 4 constituent anion main
Chemical bonds
  Bond Number
$ >Al-O-$ 6
$\geq Si-O-$ 4
$\cdot Ca^{2+} \cdot O^{-}-$ 4
Oxides
Formula $CaO$ $Al_{2}O_{3}$ $SiO_{2}$
Mass fraction (%) 40.9 37.18 21.91

Strunz

Class
silicates (09)
Division
sorosilicate (09.B)
Family
Si2O7 groups, without non-tetrahedral anions; cations in tetrahedral [4] and greater coordination (09.BB)
Code
09.BB.10

Dana

Major class
silicates (VIII)
Class
sorosilicate Si2O7 groups, generally with no additional anions (55)
Type
with cations in [8] and lower coordination (55.04)
Group
Melilite group (55.04.01)
Code
55.04.01.02
Phase type
crystalline
Crystal system
tetragonal
Crystal class
scalenohedral
Crystal class symbol
-42m (D2d)
Crystal spacegroup
P-42(1)m
Molar mass
274.20 $g/mol$
Density
2.9 - 3.07 $g/cm^3$
State NTP
solid
Refringence type
uniaxial
Refringence sign
negative
Birefringence
0.0100
Refraction index $n_o$ (w)
1.67
Refraction index $n_e$ (e)
1.66
Pure color
colorless
Color
brown, colorless, greenish, gray, yellow
Diaphaneity
transparent to translucent
Luster
vitreous
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