THE ORIGIN OF FOLIATED CRYSTALLINE ROCKS 240 
stone of Grenville,’ Ont., large crystals of zircon with well-developed 
faces have been found. They are associated with graphite, wollas- 
tonite and titanite and were probably formed through the action of 
intrusives. The evidence here seems to show that zirconium is 
capable of being carried in solution some distance from the main 
body of the intrusive. 
At Rib Hill, Wausau, Wis., there is a quartzite which is cut by 
granite and which contains abundant zircons, many of which exhibit 
Fic. 5.—Secondary enlargement of zircon. 180 
secondary enlargement. A microphotograph of one of these grains 
is shown in Fig. 5. The new material has been added largely to 
the ends of the grains, usually forming pyramidal faces terminated 
by the basal pinacoid, though the latter is sometimes absent. In 
one case the new growth was observed to completely envelop the 
original grain. This suggests that the material for the later 
crystallization was, in part at least, introduced from without and 
field relations seem to point to the granite as the source. 
*C. Hoffmann, Ann. Rep. Geol. Surv. Can., IV, N.S. (1890), 66T. 
