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!
Smith (1969) has showed that the "pseudobrookite" from Havredal in fact consists of an extremely fine-grained mixture of hematite and rutile with a lesser amount of quartz and chlorite