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!
Cooper & Stanley (1990): "Occurs in large lenses up to 3m across (averaging 0.5m) separated by barren ground. [...] Unremarkable white cockscomb aggregates have been found in the Endeavour level (King Collection, National Museum of Wales, Cardiff)."