English: Yellow brown partially melted crystal of the very rare Fe chloride mineral rokühnite from the type locality in Hildesheim, Germany (Hildesheim, Lower Saxony, Germany). Analyzed specimen by SEM/EDS. The mineral species is very higroscopic, from Mindat: water-soluble; topotactical hydration and rapid oxidation in air. okuhnite is described as light green, but rapidly oxidizes and turns brown when exposed to air and moisture. Ex Vandenbroucke Museum collection from Waregem, Belgium.