Chemical composition of manganese bog ore from the Glitrevatn (Lake Glitre) in Norway

South of Glitrevatn (Lake Glitre), 40 km NNW from Oslo (formerly Kristiania), lies an important intrusive quartz-porphyry formation as part of the Drammen granite massif. In all the valley lowlands cutting out of this formation and leading to Glitrevatn, one finds important deposits of manganese rich bog ore. On the relief upstream side, these deposits are overlain by a moraine talus made of debris originated from the granitic formation. The deposit itself is two to three meters thick and made internally of an alternance of iron and manganese rich layers. The author has made the hypothesis that the granitic formation is the source of the metals.