Mineral phase
IMA name
Nepheline
Secondary names
Nephelite; Elaeolite
Type
Class
silicate mineral
Compound type
tektosilicate
Chemical composition
Formula
$Na_3K(Al_4Si_4O_{16})$
Chemical formula
Na3K(Al4Si4O16)
Elemental formula
Na3 K Al4 Si4 O16
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Na$ Sodium element 3 constituent element main
$K$ Potassium element 1 constituent element main
$Al$ Aluminium element 4 constituent element main
$Si$ Silicon element 4 constituent element main
$O$ Oxygen element 16 constituent element main
Composition comments
former formula: $(Na,K)AlSiO_4$ - Common Impurities: $Mg, Ca, H_2O$
Oxides
Formula $Na_{2}O$ $K_{2}O$ $Al_{2}O_{3}$ $SiO_{2}$
Mass fraction (%) 15.91 8.06 34.9 41.13

Strunz

Class
silicates (09)
Division
tektosilicate without zeolitic H2O (09.F)
Family
Tektosilicates without additional non-tetrahedral anions, (Al,B):Si = 1:1 (09.FA)
Code
09.FA.05

Dana

Major class
silicates (VIII)
Class
tectosilicate Al-Si framework (76)
Type
Feldspathoids and related species (76.02)
Group
Nepheline group (76.02.01)
Code
76.02.01.02
Phase type
crystalline
Crystal system
hexagonal
Crystal class
pyramidal
Crystal class symbol
6 (C6)
Crystal spacegroup
P6(3)
Comments
there are 3 cavities with oval outline and 1 cavity with hexagonal outline: the former are occupied by sodium, the latter by potassium
Molar mass
584.33 $g/mol$
Density
2.55 - 2.66 cal.: 2.64) $g/cm^3$
State NTP
solid
Refringence type
uniaxial
Refringence sign
negative
Birefringence
0.0030 - 0.0050
Refraction index $n_o$ (w)
1.531 - 1.549
Refraction index $n_e$ (e)
1.528 - 1.544
Pure color
colorless
Color
white, gray, brown, brownish gray, reddish white
Diaphaneity
transparent to opaque
Luster
vitreous
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