mineral
Feldspar
KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8 (Feldspar group)
AI-generated identification · may be incorrectMohs 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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Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Granite
Granite (Phaneritic intrusive igneous rock)
igneous
Calcite–fluorite mineral specimen with iron-oxide staining
Calcite (CaCO₃), likely fluorite (CaF₂), with possible quartz and iron/manganese oxides
mineral