albite n : a widely distributed rock-forming feldspar [syn: white feldspar]

English

Etymology

From the Latin albus (white), the common color of the mineral.

Noun

albite (plural: albites)

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.

See also

• feldspar
• quartz monzonite
• rock

Albite is a plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. As such it represents a plagioclase with less than 10% anorthite content. The pure albite endmember has the formula NaAlSi3O8. It is a tectosilicate.

Albite crystallizes with triclinic pinacoidal forms. Its specific gravity is about 2.62 and it has a Mohs hardness of 6 - 6.5. Albite almost always exhibits crystal twinning often as minute parallel striations on the crystal face. Albite often occurs as fine parallel segregations alternating with pink microcline in perthite as a result of exolution on cooling. It occurs in granitic and pegmatite masses, in some hydrothermal vein deposits and forms part of the typical greenschist metamorphic assemblage for rocks of originally basaltic composition.

It was first reported in 1815 for an occurrence in Sweden. The name is from Latin, albus for the typical white color.

References

• Mindat data
• Webmineral data
• Mineral galleries