Feldspar

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Feldspar
Feldspar-Group-291254.jpg
Feldspar crystal (18×21×8.5 cm) frae Jequitinhonha valley, Minas Gerais, Sootheastren Brazil.
General
Category tectosilicate
Formula
(repeating unit)
KAlSi3O8NaAlSi3O8CaAl2Si2O8
Identification
Color pink, white, gray, broun
Crystal seestem triclinic or monoclinic
Twinnin tartan, carlsbad, etc
Cleavage twa or three
Fractur alang cleavage planes
Mohs scale hairdness 6.0-6.5
Luster Vitreous
Streak white
Diaphaneity opaque
Specific gravity 2.55 - 2.76
Density 2.56
Refractive index 1.518-1.526
Birefringence first order
Pleochroism none
Ither characteristics exsolution lamellae common
References [1]

Feldspars (KAlSi3O8NaAlSi3O8CaAl2Si2O8) are a group o rock-furmin tectosilicate minerals that mak up as much as 60% o the Yird's crust.[2]

Feldspars crystallize frae magma as veins in baith intrusive an extrusive igneous rocks an are an aa present in many types o metamorphic rock.[3] Rock furmed almaist entirely o calcic plagioclase feldspar is kent as anorthosite.[4] Feldspars are an aa foond in mony types o sedimentary rock.[5]

References[eedit | eedit soorce]

  1. "Feldspar". Gemology Online. Retrieved 8 November 2012. 
  2. Feldspar. What is Feldspar? Industrial Minerals Association. Retrieved on July 18, 2007.
  3. "Metamorphic Rocks." Metamorphic Rocks Information. Retrieved on July 18, 2007
  4. Blatt, Harvey and Robert J. Tracy, Petrology, Freeman, 2nd ed., 1996, pp. 206–210 ISBN 0-7167-2438-3
  5. "Weathering and Sedimentary Rocks." Geology. Retrieved on July 18, 2007.