Barite and limonite crystals. Intertwined tabular crystals of barite (white) partially overgrown with a yellow brown encrustation of limonite. Barite is a barium sulphate mineral and is the main source of barium. Limonite is an important iron-bearing ore. It is not a true mineral but is a mixture of similar iron oxide and hydroxide minerals, including goethite, lepidocrocite and jarosite. This sample is from the Winterberg quarry, Bad Grund, Harz mountains, Germany.