Constituent
- Name
- Anorthite
- IMA name
- Albite-Anorthite series
- Class
- silicate mineral
- Compound type
- tektosilicate
- Comments
- Plagioclase is a wider series of the feldspar group
- Relevance
- main - major
- Arrangement
- single phase
- Mass fraction
- 1.0
- Formula
- Chemical formula
- ((Na)x(Ca)1-x)((Al)1-x(Si)x)AlSi2O8
- Elemental formula
- (Na)0-1 (Ca)0-1 (Al)1-2 (Si)2-3 O8
- Isotope mixture type
- terrestrial abundance
- Composition comments
- Common replacement: K (limited solid solution) - Common impurities: Ti, Fe, Mg, H2O
- Oxides
-
Formula 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
- crystalline
- Crystal system
- triclinic
- Crystal class
- pinacoidal
- Crystal class symbol
- -1 (Ci)
- Crystal spacegroup
- P-1
- Molar mass
- 263.02 - 277.41
- Density
- 2.61 - 2.76
- Refringence type
- biaxial
- Refringence sign
- positive or negative
- Birefringence
- 0.009 - 0.012
- Refraction index
- 1.528 - 1.576
- Refraction index
- 1.532 - 1.583
- Refraction index
- 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