Oligoclase vs. Plagioclase

A white, gray, green or red variety of plagioclase feldspar that contains a higher proportion of sodium than calcium and is common in silica-rich igneous rocks.

(mineral) Any of a group of aluminum silicate feldspathic minerals ranging in their ratio of calcium to sodium.

(mineral) 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.

A general term used of any triclinic feldspar. See the Note under Feldspar.

A triclinic soda-lime feldspar. See Feldspar.

Any of a rock-forming series of triclinic feldspars

Any of a rock-forming series of triclinic feldspars