Regional Report: Utö Island, Haninge, Stockholm, Södermanland, Sweden

A classical locality. Several granitic proterozoic pegmatite dikes transects the rocks of the northern part of the Utö Island. Some of these can be classified as LCT pegmatites of the petalite subtype. 2 famous classical LCT pegmatite bodies- the first ones to be recognized as litium pegmatites- transects a sequence of rhyolitic metatuffites, skarns and BIF in old iron mines. These 2 LCT pegmatites are the typlocality for 4 species: spodumen, petalite, tantalite-(Mn) and holmquistite. The element lithium was also discovered in petalite from Utö. The iron mines were opened in the 12th century and closed down in 1878. Minor silver mining took also place during the 17th century. The pegmatites were best exposed in the open pit of the Nyköpingsgruvan mine. Today pegmatite materiale can best be found on the several dumps from the iron mines. Beside minerals from the primary phases like microcline, albite, petalite, spodumene etc, also interesting late-stage paragenesis minerals (beryllosilicates and others) can be found in small cavities, cracks and fracture infillings in the materiale found at the dumps.

For full locality listing click here. Alternatively: Click here for heirarchical list of localities in Utö Island, Haninge, Stockholm, Södermanland, Sweden