The Mineral Resources of Greenland. 23 
and form only upon fractures. The white and “black” varieties occur 
in irregular bunches within one another without apparent rule although 
in certain portions they and siderite are rudely banded parallel to the 
walls of the mass. The black cryolite is radio-active!). As impurities 
in the cryolite mass is considerable light brown siderite, some white 
Fig. 10. Micropegmatite-like intergrowth of cryolite and microcline. 
Natural size. 
С = Cryolite. М = Microcline. Q = Quartz. Р = Pyrite. G = Galena. 
quartz, and less zinc blende, galena, chalcopyrite and pyrite. These 
impurities usually make up about 10 % of the ore, although they may 
locally be practically absent or make up almost all of the body. Siderite 
occurs not only as scattered crystals through much of the cryolite, but 
also forms large masses alone or with the other impurities: in such 
bodies its crystal faces may be 7.5 em (three inches) across. Such large 
masses of siderite and other impurities are not mined. The zinc blende 
is reported to carry about 7 % iron. The galena is argentiferous, car- 
1) JarL: Fabriken Øresund Pages 8—9. 1909. 
