“A polished section from the Geological Survey of Finland's collections, donated by Professor Uytenbogaart and Committee for the Summer School of Cambridge in 1963. GTK gratiously offered to borrow this set of 9 polished epoxy mounts. This sample is labeled "SS 17, Arsenopyrite-rich ore of Type B. Boliden, Sweden" Off-white phase is variously oriented arsenopyrite, yellow phase is chalcopyrite, dark grey phase silicate, and light grey phase is sphalerite with classic "chalcopyrite disease". Plane-polarised reflected light.”