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!
Kingsbury reference. Kingsbury & Hartley (1957): "yellow to greenish-yellow, powdery beaverite, with beudantite and other secondary arsenates in oxidized vein material from a north-west-south-east vein, carrying Pb-Zn-Fe-As-Cu sulphides, tried from an old cross-cut near its outcrop between Sandbed and Potts Gill mines."
"Yellow powdery aggregates, with earthy brown beudantite and plumbojarosite, in similar vein-material from an old level, half a mile to the north-west of and probably driven on the same vein as the preceding, near the farm of Nether Row."