48 Sypney H. BALL: 
406 tons of concentrates were produced. Flake graphite disseminated 
in gneiss is the commonest type of graphite deposit in Greenland and, 
in the aggregate, such deposits contain an enormous amount of graphite. 
With depth, pyrite will replace the limonite. Only exceptionally rich, 
graphite-bearing granite gneisses are apt to be of commercial import- 
ance, due to the expense and difficulty of concentrating clean graphite, 
particularly a product free from biotite. 
Microscopic examination shows the rocks of these deposits to be 
Fig. 20. Graphite bearing granite schist. 
Sungausak (Arfersiorfik fiord) graphite blades (black) cutting other 
constituents. Microcline (M), ortoclase (0), plagioclase (P), quartz (Q) 
and biotite (B). Magnified 60 times. 
schistose granite gneisses or granite schists composed principally of 
quartz, orthoclase, biotite and graphite, with garnet and sillimanite 
usually abundant. Sodic plagioclase, microcline and zircon are present 
in some thin sections. The graphite occurs characteristically in parallel 
intergrowths with biotite and less commonly with sillimanite; in part 
it replaces biotite, either in irregular masses or around the border; it 
also occurs in small masses enclosed in quartz, felspar and garnet; in 
rare instances, it replaces felspar; and it rather commonly occurs ın 
unoriented blades in the highly gneissic rock, either cutting several of 
the other constituents or in fractures in them (Fig. 20). The majority 
