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!
Stanley & Vaughan (1981: 258-259): "in three forms: (i) as relatively large grains (< 100µm) commonly enclosed in argentian tetrahedrite; (ii) along cleavages in galena, with chalcopyrite and minor tetrahedrite, possibly the result of post-cleavage remobilization; (iii) as intergrowths in galena, either as platelets or rods, usually no more than a few microns in width and clearly oriented along structural planes of the galena, or as rounded blebs (< 5-10 µm) arranged in irregular curved strings, possibly along galena grain boundaries. Irregular grains of bournonite (20-30µm) also occur either associated with native antimony or as somewhat smaller grains at chalcopyrite/galena grain boundaries."
