The Nyköpingsgruvan pegmatites are located on the northern part of Utoe Island, Sweden, and consist of two pegmatite bodies that transect the Nykoepingsgruvan iron formation.
During crystallization, tourmaline composition evolves from Al-rich schorl through elbaite and phases intermediate between elbaite and rossmanite to Ca-bearing elbaite-rossmanite and finally to Ca-bearing elbaite.
Selway, Julie B.; Smeds, Sten-Anders; Cerny, Petr; Hawthorne, Frank C.
Compositional evolution of tourmaline in the petalite-subtype Nykopingsgruvan pegmatites, Uto, Stockholm Archipelago, Sweden.
(2002), 124, 93-102.
Selway JB, Smeds S-A, Cerný P, Hawthorne FC (2002) Compositional evolution of tourmaline in the petalite-subtype Nyköpingsgruvan pegmatites, Utö, Stockholm archipelago, Sweden. GFF, 124(2):93–102.