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Alternative forms 
feldspar (plural feldspars)
- (mineralogy) Any of a large group of rock-forming minerals that, together, make up about 60% of the earth's outer crust. The feldspars are all aluminum silicates of the alkali metals sodium, potassium, calcium and barium. Feldspars are the principal constituents of igneous and plutonic rocks.
Related terms 
Derived terms 
any of a large group of rock-forming minerals