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!
Kingsbury reference. Bridges et al. (2011): "The Kingsbury Collection in the NHM contains a single specimen of gold labelled from the 90-fathom level dumps of Roughton Gill Mine and claimed to have been collected in 1960. It consists of a small area of hackly gold in a brown quartz matrix with grey copper sulphide oxidising to malachite. The specimen has obviously been broken into at least two parts, but there is no sign of the remainder of the specimen in the collection. Grey copper sulphides are rare at Roughton Gill, the specimen does not look typical of the site and no other collector has found gold here. This specimen must be considered fraudulent."
