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!
Bridges et al. (2011): "Eastwood (1921) notes that the pigment umber was worked at Roughton Gill Mine from the dumps, although there is some doubt about this since the main dumps seem to be undisturbed. Cooper and Stanley (1990) note the presence of ‘limonite’. Brown stains and crusts of limonitic ochres are very abundant on dump material and are probably mostly goethite. Rarely it is found as pseudomorphs of small pyrite crystals and saddle-shaped crystals of dolomite up to 0.5 mm long. Less common are very dark brown to black botryoidal crusts which can reach 3 mm in thickness."
