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!
Meikle (1989): "Covellite is very rare at Boyleston Quarry. It is found on prehnite, as small blue-black to indigo blue, dull metallic, hexagonal crystals «0.5 mm). Some crystals are truncated by pyramidal terminations. Occasionally it is partly coated with chrysocolla, as well as being accompanied by chrysocolla crystals pseudomorphous after covellite, along with small hemispheres and spherules (<0.5 mm) of malachite."
