Meta-BIF (meta-banded iron formation) (6.3 cm across) from the Precambrian of Sweden.
This strongly magnetic rock is a multiply-metamorphosed banded iron formation that comes from the waste rock piles of old Swedish iron mines (active from the 1100s to the late 1870s).
The rock is composed principally of magnetite, epidote, holmquistite amphibole, and carbonate. Holmquistite is a rare amphibole that contains lithium - it's chemical formula is Li2Mg3Al2Si8O22(OH)2 - lithium magnesium hydroxy-aluminosilicate. On this rock's top surface, the holmquistite consists of very dark bluish needles, best seen near the lower left corner. This particular rock comes from the type locality for holmquistite.
This rock has been metamorphosed more than once. A previously-existing meta-BIF was contact metamorphosed by intrusion of Nyköpingsgruvan pegmatitic granites and lithium pegmatites during the late Paleoproterozoic, at 1.8 Ga.
Locality: spoils piles at Utö Mines, Utö, Stockholm Archipelago, Haninge Municipality, Stockholm County, eastern coastal Sweden.
Reference on the geology of Utö, Sweden:
Mansfeld, J. 2012. The Geology of Utö, Excursion Guide. 9 pp.
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