8 Sypney H. BALL: 
are Tertiary basalt and andesite flows, beneath which, in places, are 
Cretaceous and Miocene sandstone, shale and coal beds. Locally these 
sedimentary rocks rest upon Cretaceous or pre-Cretaceous basalt flows, 
but they usually lie upon a hilly surface of pre-Cambrian gneiss. Pleisto- 
cene river and marine gravels, and morainal material are comparatively 
unimportant. In a broad way, the geology of the east coast 1$ similar, 
although sedimentary rocks are more common. 
Large bodies of granite gneiss, hornblende gneiss and granite 
without other associated rocks, are not known to contain ore deposits, 
although granite gneiss is frequently graphite-bearing. The diabases 
Fig. 6. Diagram showing relations of Greenland rocks. 
1. Mica and graphitic schists and Jimestone. 2. Hornblende gneiss. 3. Granite gneiss. 4, Amphibolite. 
5. Crystalline limestone. 6. Dunite. 7. Granite and pegmatite. 8. Diabase. 9. Red sandstone of Devo- 
nian (?) age. Julianehaab region: 10. Soda syenites. 11. Trachyte lavas. 12. Pre-Cretaceous basalts. 
13. Cretaceous and Tertiary sandstone shale, and coal: Disco Island region: 14. Miocene (?) peridotite. 
15. Miocene basalt. 
and the younger sedimentary rocks are also barren. The other rocks 
are more favorable. 
The deposits of economic minerals associated with all except the 
Cretaceous and Miocene rocks are presumably either magmatic segrega- 
tions, pneumatolitic deposits, or veins formed by waters of magmatic 
origin at great or fairly great depth. Magmatic segregations are not 
commercially important, but the native iron and the graphite of the 
basalt of the Disco Island region, the chrome iron ores of the dunites 
and the nickeliferous pyrrhotite of the Nugsuak peridotites and Disco 
Island basalts are genetically interesting. 
The most important of the pegmatitic bodies are the Ivigtut cryo- 
lite and certain of the graphite deposits. Molybdenite is also a pegmatitic 
mineral of wide distribution. Other pegmatitic minerals include wol- 
framite, muscovite, cassiterite, magnetite, ilmenite, garnet, fluorspar, 
fergusonite, columbite, cordierite, and semi-precious varieties of felspar. 
The minerals of the pegmatites of the soda-rich rocks of the Juliane- 
haab district include willemite, zincblende, fluorspar, and many minerals 
containing the rare earths and metals. Bornite and chalcopyrite in 
small amounts also occur in granite-pegmatite, but the larger of the 
