A primary constituent in sodium-rich alkalic volcanics, pegmatites, and other silica-poor igneous rocks.
Valid Species (Pre-IMA) 1865
Notable studied occurrences include: at Naujakasik, near the Tunugdliarfik Fjord, and on the Kangerdluarssuk Plateau, in the Ilimaussaq intrusion; from Narssarssuk; and elsewhere in Gr
Link to MinDat.org Location Data.
From the Greek for riddle, apparently an allusion to its (formerly) uncertain chemical composition.