Mandarinoite is a very rare hydrated iron, selenium oxide. Blades of green to yellow mandarinoite richly cover the sulfide matrix on this fine and rarely available material from the El Dragon Mine of Bolivia. This very small mine has produced over 20 selenium-bearing minerals from a single, up to 6 cm wide vein. See the Mineralogical Record article in Volume 21, Number 2, March-April 1990, pp. 133-146.