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, an abundant group of rock-forming minerals which constitute 60% of the earth's crust. Chemically the feldspars are silicates of aluminum, containing sodium, potassium, iron, calcium, or barium or combinations of these elements.
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An apple-green, bright-green, or blue-green variety of microcline found in the United States and the former Soviet Union; sometimes used as a gemstone. Also known as amazon stone.