Open main menu

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

Feldspar
Feldspar-Group-291254.jpg
Feldspar crystal (18×21×8.5 cm) frae Jequitinhonha valley, Minas Gerais, Sootheastren Brazil.
General
Categorytectosilicate
Formula
(repeatin unit)
KAlSi3O8NaAlSi3O8CaAl2Si2O8
Creestal seestemtriclinic or monoclinic
Identification
Colourpink, white, gray, broun
Twinnintartan, carlsbad, etc
Cleavagetwa or three
Fracturalang cleavage planes
Mohs scale haurdness6.0-6.5
SkinkleVitreous
Streakwhite
Diaphaneityopaque
Speceefic gravity2.55 - 2.76
Density2.56
Refractive index1.518-1.526
Birefringencefirst order
Pleochroismnone
Ither chairacteristicsexsolution lamellae common
References[1]

Feldspars crystallize frae magma as veins in baith intrusive an extrusive igneous rocks an are an aa present in mony 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]

ReferencesEedit

  1. "Feldspar". Gemology Online. Retrieved 8 November 2012. 
  2. Feldspar. What is Feldspar? Industrial Meenerals 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.