Noun

1. A plagioclase feldspar, the first member of the Albite-Anorthite solid solution series. Primarily a mineral of plutonic rocks, also found in pegmatites. When Albite substitutes for a potassium feldspar in granite, the rock is called quartz monzonite.

• Chemical composition: Sodium aluminum silicate, $NaAlSi\_3O\_8$

• Physical properties:
  • Moh's Hardness: 6.0
  • Specific gravity: 2.63
  • Color: white, sometimes with a bluish cast
  • Luster: glassy
  • Fracture: conchoidal
  • Cleavage: two good at about 94º to each other
  • Habit: Triclinic - pinacoidal. Usually twinned and striated. The striations are visible to the naked eye, and are characteristic of plagioclase feldspars in general and Albite in particular.