Constituent
Name
Plagioclase Ab86
IMA name
Albite-Anorthite series
Class
silicate mineral
Compound type
tektosilicate
Comments
Plagioclase is a wider series (Na,Ca)(Si,Al)4O8 of the feldspar group
Relevance
main - major
Arrangement
homogeneous in multi-phases
Mass fraction
0.113 ± 0.004
Formula
(Na0.86,Ca0.14)(Al0.14,Si0.86)AlSi2O8
Chemical formula
((Na)0.86(Ca)0.14)((Al)0.14(Si)0.86)AlSi2O8
Elemental formula
Na0.86 Ca0.14 Al1.14 Si2.86 O8
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
Na Sodium element 0.86 1.0 constituent element main
Ca Calcium element 0.14 1.0 constituent element main
Al Aluminium element 1.14 1.0 constituent element main
Si Silicon element 2.86 1.0 constituent element main
O Oxygen element 8 1.0 constituent element main
Composition comments
Common replacement: K (limited solid solution) - Common impurities: Ti, Fe, Mg, H2O
Oxides
Formula Na2O CaO K2O Al2O3 SiO2
Mass fraction (%)

Strunz

Class
silicates (09)
Division
tektosilicate without zeolitic H2O (09.F)
Family
without additional non-tetrahedral anions, (Al,B):Si = 1:1 (09.FA)
Code
09.FA.35

Dana

Major class
silicates (VIII)
Class
tectosilicate Al-Si framework (76)
Type
with Al-Si frameworks (76.01)
Group
Plagioclase series (76.01.03)
Phase type
amorphous
Crystal system
amorphous
Crystal class
pinacoidal
Crystal class symbol
-1 (Ci)
Crystal spacegroup
P-1
Molar mass
263.02 - 277.41 g/mol
Density
2.61 - 2.76 g/cm3
Refringence type
biaxial
Refringence sign
positive or negative
Birefringence
0.009 - 0.012
Refraction index nα
1.528 - 1.576
Refraction index nβ
1.532 - 1.583
Refraction index nγ
1.538 - 1.588
Dispersion V
weak to relatively weak
Color
white, gray, bluish white, reddish white, greenish white
Diaphaneity
transparent to subtranslucent
Luster
vitreous