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 three forms on specimens collected by D.R. Middleton from dumps of the old workings near the head of the gill."
Habit:
sheafy aggregates of acute rhombohedral crystals to 2 mm, partially embedded in massive beudantite on quartz; and minute (< 1 mm) brownish crystals of pseudo-octahedral aspect resulting from the equal development of the pinacoid and a rhombohedron. On this latter habit the rhombohedron faces are lustrous whilst the pinacoids are dull; these characters show that the habit is not an isometric octahedron (det. BM(NH): XRD).
