noun. a widely distributed feldspar that forms rocks.
1. Noun, singular or mass Search for moonstone in areas where a high concentration of albite. 2. Adjective Sedimentary rocks made of pebbles, sand and combinations of quartz and plagioclase feldspars (albite, labradorite) create rocks that appear white to dark gray, sometimes black. 3. Adverb One type of moonstone is a composite mineral, made up of orthoclase and albite, two types of feldspar, and other mineral cousins also called moonstones are composed of labradorite and larvikite.