- a feldspar mineral of the plagioclase group, often characterized by a brilliant change of colors, with blue and green most common.
- a blue, green, or reddish-brown feldspar mineral of the plagioclase series: used as a decorative stone. Formula: CaAl 2 Si 2 O 8 .NaAlSi 3 O 8
- A blue, gray, green, or brown triclinic mineral that is a variety of plagioclase feldspar. It occurs in igneous rocks.