PREFACE. 



The three mining areas, viz. : Sudbury, Cobalt, and Porcu- 

 pine, that are described in this Guide Book, are the most 

 important in the Province of Ontario. Sudbury is the 

 world's greatest producer of nickel and is also an important 

 producer of copper. Minor quantities of platinum, palla- 

 dium and other metals have been obtained from its ores. 

 Cobalt leads all other areas in the world in its output of 

 silver and of cobalt, and arsenic and nickel occur in import- 

 ant quantities in its ores. Porcupine, the product of 

 which is gold, is a comparatively new mining area and 

 is only partly developed. The two chief mines, however, 

 are splendidly equipped, and during the last year have been 

 important producers. Other mines at Porcupine have re- 

 cently begun milling operations. 



As nearly as can be determined from Government reports, 

 Sudbury had produced, in round numbers, 158,000 tons of 

 nickel and 103,000 tons of copper by the end of 1912. 

 Statistics of by-products — platinum, palladium, and other 

 metals — are incomplete. At the same date, cobalt had pro- 

 duced approximately 156,000,000 ounces of silver. In 1912, 

 owing to the Porcupine production, the gold output of 

 Ontario had a value of $1,859,285, compared with $42,637 

 in 1911. 



The ore deposits of all three of the areas are in rocks that 

 are classified as of pre-Cambrian age, and are believed to 

 owe their origin to igneous intrusions. At Sudbury the 

 intrusive rock, described on following pages, is quartz- 

 norite, at Cobalt quartz-diabase, and at Porcupine granite. 



Sudbury is about 90 miles to the southwest of Cobalt, and 

 it is believed that the norite of the one area and the quartz- 

 diabase of the other are genetically connected. The close 

 chemical relations of the two rocks are described in the 

 following pages devoted to the Cobalt area. 



The colored geological map, on a scale of eight miles to 

 the inch, that accompanies this guide book, shows the 

 geology of the three areas in so far as it is at present 

 known. Larger scale maps have been published and are 

 referred to in the text. 



