ROCKS OF THE APATITE REGION. 



97 



In its geological structure the region consists of alternating bands of 

 gneiss, crystalline limestones and pyroxenic rocks, in which are inter- 

 stratified a number of zones of quartzites, rust-colored rock or fahlbands, 

 and several horizons of magnetic iron ore. These rocks all belong to the 

 Grenville series, the uppermost of the two main divisions into which the 

 Laurentian system is now quite generally divided. 



OT TA WA C O UN 



CANADA. 



^^^Q.neiss Hr. 

 - EIEISEGineiss n 



Figure i. — The Apatite Region of Ottawa County^ Canada. 



The Grenville series includes rocks of very different petrographical 

 development and of great variability in mineralogic composition. " In 

 it are found all the mineral deposits of economic value — apatite, iron ore, 

 asbestos, etcetera — which occur in the Laurentian."^ 



Apatite is found quite generally throughout the series, but the princi- 

 pal workable deposits occur in a belt (see IV, figure 1) of rust-colored 



* Journal of Geology, vol. i, No. 4, p. 327. 



