mineral
Feldspar
KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8 (Feldspar group)
Mohs hardness 6.0-6.5, vitreous to pearly luster, perfect two-direction cleavage at nearly 90 degrees, color varies from pink, white, reddish-brown to gray, monoclinic or triclinic crystal structure.
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Physical properties
Mohs hardness 6.0-6.5, vitreous to pearly luster, perfect two-direction cleavage at nearly 90 degrees, color varies from pink, white, reddish-brown to gray, monoclinic or triclinic crystal structure.
Formation & geological history
Forms primary crystallization in igneous rocks (granite, basalt), regional metamorphic rocks (gneiss, schist), and sedimentary deposits.
Uses & applications
Extensive industrial use in ceramics, glassmaking, mild abrasives, and as a gemstone (e.g., moonstone, amazonite, sunstone).
Geological facts
Feldspars make up about 60% of Earth's crust. The name derives from the German 'Feldspat', meaning 'field spar'.
Field identification & locations
Identified by its blocky shape, distinct right-angle cleavage faces, vitreous luster, and hardness of 6. Commonly found in granitic terrains worldwide.
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Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
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Limonite / Goethite (Iron Ore Mineral nodule)
FeO(OH)·nH2O / FeO(OH)
mineral
Schist
Schist
Metamorphic
Septarian Pebble
Septarian nodule / Concretion
sedimentary
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
mineral
Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary