oligoclase

Plural: oligoclases

Noun

• any of a series of triclinic feldspars that form rocks
• A plagioclase feldspar, the second member of the Albite-Anorthite solid solution series. Primarily found as small crystals in impure marble. Oligoclase contains a small amount of calcium substituting for some of the sodium in its formula. Oligoclase with reddish-golden inclusions found in Norway and Canada is called sunstone.

Synonyms

plagioclase

Related Words

feldspar, plagioclase, rock