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!
Mostly a rock-forming mineral, as coarse, white grains in the outer zones of the pegmatite. But also as a very late crystallizing K-rich variety (described by Jenks 1935), very fine-grained and tan colored with cleavelandite in the inner mineralized zone. The K-rich variety forms tiny, tabular, rhombic crystals or saw-toothed overgrowths on cleavelandite in numerous small pockets in this zone.
Habit:
primary crystals blocky, complex, striated. Secondary ones tabular, rhombic, as druses or overgrowths
Strickland Quarry, Strickland pegmatite, Collins Hill, Portland, Middlesex County, Connecticut, USA