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 golden-yellow and golden-brown powdery aggregates on cerussite and altered galena in the outcrop of the vein, associated with other minerals beudantite -> beaverite and beudantite -> plumbojarosite."