Glaskopf

A generic term actually referring to any botryoidal mineral, but mostly used for botryoidal varieties of iron and manganese oxides. Depending on the colour, Schwarzer Glaskopf (black), Brauner Glaskopf (brown) and Roter Glaskopf (red) (= kidney ore) are distinguished. The latter is usually hematite while the first two generally consist of goethite/limonite, sometimes with minor lepidocrocite.