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. Cooper & Stanley (1990): "Kingsbury & Hartley (MS) list brochantite from 'Todd Gill'; Kingsbury (MS1) gives the locality as 'just east of Roughton Gill lead works. Old cross-cut at the foot of the gill, driven on the north vein', i.e. probably the Mexico mine Low level."