576 EDWARD STEIDTMANN 



CirkeP states the Amherst graphite deposits occur as lenticular 

 masses and pockets, disseminations, and veins in eruptive rock 

 intrusive into the Grenville limestones. Graphite occurs within 

 feldspar, quarts, and pyroxene. It is mostly associated with 

 feldspar or pyroxene, less frequently with calcite and woUastonite. 

 Garnet, zircon, scapolite, titanite, muscovite, pyrite, apatite, 

 leucoxene, biotite and monazite are accessory minerals of the 

 gangue. 



Dulieux^ reports that the rocks of the Lake Chibogomon region, 

 north of Lake St. John, in Quebec, constitute an isolated belt of 

 diabases and gabbros and rocks derived from them; viz., chloritic, 

 epidotic, talc schists, and serpentine, surrounded by Laurentian 

 granites and gneisses, the backbone of Labrador. They contain 

 deposits of cupriferous and auriferous sulphides, magnetic iron, 

 and asbestos. 



Wilson^ finds that the pre-Cambrian rocks in western Quebec 

 between 75° 30' and 79° 30' west longitude and 48° and 49° north 

 latitude include hornblende schists, chlorite schists, diabase, and 

 porphyries, all probably of Keewatin age, and Laurentian granites 

 and gneisses. 



VI. THE CORDILLERAS 



Ball'* finds that the pre-Cambrian, magnetic, titaniferous iron 

 ores of Iron Mountain in southeastern Wyoming form a series of 

 dikes cutting anorthosi:e. Granitic masses dissect both. The ores 

 and the anorthosite contain the same minerals with some minor 

 exception, but in different proportions. The tonnage of ore is large, 

 averaging high in iron, and probably low in phosphorus, but too 

 high in titanium to be desirable under present conditions. 



'Fritz Cirkel, "The Amherst (Quebec) Graphite Deposits," Quart. Bull. Can. 

 Mining Inst., 1910, pp. 107-15. 



^ E. Dulieux, "The Chibogomon Region, Quebec," Jour. Can. Min. Inst., XII 

 (1909), 184-93. 



3 W. J. Wilson, "Geological Reconnaissance along the Line of the National Trans- 

 continental Railway in Western Canada," Cowa^^a Geol. Survey, Mem. 4, (1910), pp. 56, 

 5 pis., I geol. map. 



'' Sidney H. Ball, "Titaniferous Iron Ore of Iron Mountain, Wj^oming." Bidl. 315, 

 1906, pp. 206-12. 



