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Feldspar identification and geology

The most abundant mineral group in the Earth's crust, comprising framework silicates with the general formula K,Na,Ca Al,Si ₄O₈. Feldspars are divided into two main series: alkali feldspars orthoclase, microcline, sanidine rich in potassium and sodium, and plagioclase feldspars albite to anorthite forming a solid solution between sodium and calcium end members. They are essential rock-forming minerals in most igneous and many metamorphic rocks. Field: mineralogy. Example: Plagioclase feldspar is the single most abundant mineral in the Earth's crust, and the calcium-rich variety labradorite in anorthosite was the dominant rock type returned from the lunar highlands by Apollo missions.. Related terms: Plagioclase, Orthoclase, Framework silicate, Twinning.

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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.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:41.999576+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Feldspar mean in geology?
The most abundant mineral group in the Earth's crust, comprising framework silicates with the general formula K,Na,Ca Al,Si ₄O₈. Feldspars are divided into two main series: alkali feldspars orthoclase, microcline, sanidine rich in potassium and sodium, and plagioclase feldspars albite to anorthite forming a solid solution between sodium and calcium end members. They are essential rock-forming minerals in most igneous and many metamorphic rocks.
What is an example of Feldspar?
Plagioclase feldspar is the single most abundant mineral in the Earth's crust, and the calcium-rich variety labradorite in anorthosite was the dominant rock type returned from the lunar highlands by Apollo missions.
Which earth-science field uses the term Feldspar?
Feldspar is used in mineralogy.
Which terms are related to Feldspar?
Related terms in this reference are Plagioclase, Orthoclase, Framework silicate, Twinning.

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