The most abundant mineral group in the Earth's crust, making up about 60% of all rocks. Feldspars are essential constituents of igneous, metamorphic, and some sedimentary rocks. Color: White, pink, gray, green. Luster: Vitreous to pearly. Streak: White. Cleavage: Perfect in two directions at 90°. Hardness: 6-6.5. Transparency: Translucent to opaque. Crystal system: Monoclinic/Triclinic. Chemical formula: KAlSi₃O₈. Specific gravity: 2.5-2.8. Formation: Crystallizes from silicate magmas at high temperatures. The specific type depends on the magma composition and cooling rate. Common geological settings: Found in nearly all igneous rocks granite, basalt , many metamorphic rocks gneiss , and some sedimentary rocks arkose sandstone . Common look-alikes and related entries: Quartz, Plagioclase.
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Next: Fluorite — Known for its wide range of colors and perfect octahedral cleavage, fluorite is the reference mineral for hardness 4 on the Mohs scale.
White minerals — Place this specimen in a broader field-identification workflow.
Quartz vs Feldspar — Compare observable properties and safer field tests.
Sources, scope & corrections
These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.
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Last updated
2026-03-30T14:39:39.820581+00:00
Review status
Published; not independently peer-reviewed
IMA–CNMNC List of Mineral Names — International Mineralogical Association. Official mineral-name, nomenclature, and classification records.
Mineral ID Key — Mineralogical Society of America. Physical-property identification methods, repeat-testing guidance, and limitations.
The most abundant mineral group in the Earth's crust, making up about 60% of all rocks. Feldspars are essential constituents of igneous, metamorphic, and some sedimentary rocks.
How can you identify Feldspar?
Compare several properties rather than relying on colour alone. This entry records colour: White, pink, gray, green; lustre: Vitreous to pearly; streak: White; Mohs hardness: 6-6.5; cleavage: Perfect in two directions at 90°; crystal system: Monoclinic/Triclinic; transparency: Translucent to opaque. Confirm an important identification with additional field tests or qualified laboratory work.
How does Feldspar form?
Crystallizes from silicate magmas at high temperatures. The specific type depends on the magma composition and cooling rate.
Where is Feldspar commonly found?
Found in nearly all igneous rocks granite, basalt , many metamorphic rocks gneiss , and some sedimentary rocks arkose sandstone .
What is Feldspar commonly confused with?
Feldspar may be confused with Quartz, Plagioclase. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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