Oligoclase

A plagioclase feldspar with an albite : anorthite molar ratio ranging from 90 : 10 to 70 : 30. Originally described from Danvikstull, Stockholm, Södermanland, Sweden.

Structural context

Albite
Crystal System triclinicCrystal Class pinacoidalSpace Group P-1
a8.154—8.169 (8.1615)
b12.823—12.851 (12.837)
c7.124—7.139 (7.1315)
alpha93.63—94.06 (93.845)
beta116.4—116.5 (116.45)
gamma88.59—89.46 (89.025)
volume666.322—668.391 (667.3565)

Based on 2 measurements

Chemical context

Stoichiometric formulas

Oligoclase
mindat.org
  • March 13, 2023(Na,Ca)[Al(Si,Al)Si2O8]
mineralogy.rocks
  • Aug. 30, 2022(Na,Ca)[Al(Si,Al)Si2O8]
Albite
mindat.org
  • March 13, 2023Na(AlSi3O8)
IMA
  • March 13, 2023Na(AlSi3O8)
mineralogy.rocks
  • Aug. 30, 2022NaAlSi3O8

Elements recorded on EPMA

2
Al
2
Ca
2
Na
2
O
2
Si

Physical properties

ColorColor entities, recognized using a custom trained NER model
  • colorless
    • pale yellow
      • bluish
      • greenish
      • reddish
      Color noteOriginal color note from the source
      Colourless, white, very pale yellow
      White to grey, bluish, greenish, reddish, colorless
      StreakStreak entities, recognized using a custom trained NER model
        Streak noteOriginal streak note from the source
        White
        Lustre
        Vitreous
        Sub-Vitreous
        Fracture
        Irregular/Uneven
        Sub-Conchoidal
        Step-Like
        Conchoidal
        Transparency
        Transparent
        Translucent
        Tenacity
        brittle
        Hardness
        6—6.5
        Measured density
        2.63—2.66
        2.6—2.65
        Calculated density
        2.65
        2.615