composition (see galena, for instance). Left: Stannoidite displaying various colours under XPL; euhedral...Nsutite Selenium, native yes Stromeyerite Stannoidite Reflection Colour & Ø Reflectance Pleochroism...grey); Himmelsfürst Mine, Brand-Erbisdorf, Freiberg District, Erzgebirge, Sachsen, Germany (sample: Seifert);...quartz (dark grey); New Bullfrog Mine, Bullfrog District, Nye Co., Nevada, USA (sample: Witzke); PPL If...placers Kaietur Falls, Potaro River, Kangaruma District, Potaro-Siparuni Region, Guyana Chalcopyrite, |