potassium feldspar

mineral

Also known as: K-feldspar, K-spar

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July 1, 2026

Quick Summary

Potassium feldspar is a common silicate mineral found in various rocks, particularly igneous ones like granites and syenites. It is a key component of Earth's crust, making up over half of it. Potassium feldspars are part of the larger feldspar group, which also includes sodium and calcium feldspars.12

These minerals are characterized by their glassy crystals and can be found in a range of colors. They are used in manufacturing glass and ceramics, and some varieties are used as gemstones. Potassium feldspars are primarily important as rock-forming minerals, with specific types like orthoclase and microcline being common. They are distinguished from other feldspars by their chemical composition and crystal structure.132

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feldspar
Chemical composition
Microcline and orthoclase are potassium feldspars (KAlSi₃O₈), usually designated Or in discussions involving their end-member composition. Albite (NaAlSi₃O₈—usually designated Ab) and anorthite (CaAl₂Si₂O₈—An) are end-members of the plagioclase series. Sanidine, anorthoclase, and the perthites are alkali feldspars whose chemical compositions lie between Or and Ab.
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Microcline and orthoclase are potassium feldspars (KAlSi₃O₈), usually designated Or in discussions involving their end-member composition. Albite (NaAlSi₃O₈—usually designated Ab) and anorthite (CaAl₂Si₂O₈—An) are end-members of the plagioclase series. Sanidine, anorthoclase, and the perthites are alkali feldspars whose chemical compositions lie between Or and Ab.
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hydrosphere
Congruent and incongruent weathering reactions
…soil water on the mineral K-spar (KAlSi₃O₈), an important phase found in continental rocks. The reaction is
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…soil water on the mineral K-spar (KAlSi₃O₈), an important phase found in continental rocks. The reaction is
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