Feldspar is a group of minerals that are commonly found in igneous, metamorphic, and sedimentary rocks. The crossword solutions for the term feldspar include MOONSTONE (9 letters), plagioclase (11 letters), orthoclase (10 letters), KAOLIN (6 letters), anorthite (9 letters), and labradorite (11 letters). MOONSTONE is a type of feldspar that has a pearly luster and is often used in jewelry. Plagioclase is a type of feldspar that is composed of calcium and sodium. Orthoclase is a type of feldspar that is composed of potassium and aluminum. KAOLIN is a type of clay that is composed of feldspar and other minerals. Anorthite is a type of feldspar that is composed of calcium and aluminum. Labradorite is a type of feldspar that is known for its iridescent colors.