an unusual plagioclase feldspar with high calcium oxide content happening in igneous stones.
A plagioclase feldspar, the ultimate member of the Albite-Anorthite solid answer show. Anorthite is quite unusual on the planet, but loaded in moon rocks. Simply because Anorthite weathers rapidly to clay nutrients under atmospheric conditions. Good crystals have already been present lava-digested limestone obstructs erupted from Mount Vesuvius.
A mineral associated with feldspar family members, generally occurring in small glassy crystals, also a constituent of some igneous stones. It's a lime feldspar. See feldspar.
A triclinic lime feldspar, present in small transparent crystals on Mount Vesuvius, and current additionally as a constituent of some rocks. See feldspar.
rare plagioclastic feldspar occurring in many igneous stones