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!
Reported initially as mineral "F" of A. F. Woodward et al (1941) and was reported here prior to its description by Hindman from Utah; however, there was insufficient material to perform definative analysis with the state-of-the-art of the period. Occurs as a secondary mineral as crystalline films coating joint planes of the quartz monzonite porphyry and contact rock near the southern end of the commercial quarry.
Crestmore quarries, Crestmore, Jurupa Valley, Riverside County, California, USA