Figs 101 and 103. There is no comprehensive study available for the famous cryolite deposit at Ivigtut, the best account probably being the brief survey by Berthelsen and Henriksen (1975, p. 133) and the mineralogically orientated account of Karup-Moller (1973). The cryolite ore body, which has now been entirely removed by mining, originally formed an irregular mass of 50x115 m extending to a depth of 70 m. Together with a pegmatite on its western side the cryolite body lay within a stock of peralkaline granite containing a little biotite, aegirine-augite and sodic amphibole. The granite is almost entirely surrounded by an intrusive breccia zone up to 60 m wide, and another breccia body, the 'bunkebreccia', outcrops to the east, both being composed dominantly of somewhat altered country rock fragments. Several sets of doleritic and peralkaline dykes occur which are both earlier and later than the central Ivigtut intrusion. The main portion of the cryolite body consisted of cryolite-siderite rock with about 20% siderite and 1-2% of quartz and sulphides, but varying widely. To the east a siderite-rich zone underlay the cryolite and to the west a fluorite-rich zone. At deeper levels the cryolite body was separated from the granite by sulphide-bearing quartz rocks. The adjacent granite is strongly greisenized. More than 80 minerals have been identified from the cryolite body including many sulphides. Pauly (1960) estimated the temperature of formation of the cryolite-siderite rock at between 510° and 590° C, but its genesis is still unclear; origins involving foyaitic, granitic, basaltic and carbonatitic sources have all been suggested.