Vote for your favorite mineral in #MinCup26! - Sphalerite vs. Anorthite Both zinc ore Sphalerite and calcium plagioclase feldspar Anorthite have perfect cleavage that will split cleanly if you hit them with a hammer, but only one can claim a larger split of your votes!
Schooner (circa 1985) writes that "A Boston Mineral Club list of Strickland quarry minerals, dating from about 1940, describes planerite as green crusts on fractured quartz. Several pieces of that material, resembling variscite, were collected at the time; unfortunately, none is now available for study."