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): "As a yellow powder with pyromorphite, cerussite, and wulfenite in cavities in quartz from the Low level dump in Todd Gill (M.P. Cooper Collection, det. Leicester Univ.: XRD)."