98 THE ROYAL SOCIETY OF CANADA 



quartz. Under the microscope these dark grey particles of mispickel 

 can be seen irregularly scattered through the quartz. The gold, which 

 is very fine and seldom visible, is associated with the mispickel rather 

 than the pyrite." 



"The source of the gold in this unusual variety of ore is probably 

 to be sought in the diorite which shattered and carried off blocks of 

 the quartzite, while magmatic solutions introduced silica, compounds 

 of arsenic and sulphur and also gold. These materials were deposited 

 in the small fissures and also in the pore spaces of the original sand- 

 stone which became transformed to the compact quartzite or arkose 

 which now forms the ore." 



"The relation of the diorite to the Lauren tian granite is not cer- 

 tain, though the two seem more or less to blend toward the south and 

 east of the mine." 



The rock called by Dr. Coleman Laurentian is the same as that 

 for which I am using Lawson's name Algoman. 



Mr. J. A. Dresser informs me that he examined a number of 

 thin sections of the quartzite from Long Lake under the microscope, 

 and found that feldspar grains or crystals were abundant in places 

 among the quartz grains. Small crystals of arsenopyrite have been 

 introduced into these feldspar crystals, but he did not find them in the 

 quartz grains. Decomposition of the feldspars had gone too far to 

 be certain whether they were orthoclase or plagioclose. 



Eastern Ontario. In eastern Ontario Arsenopyrite and gold are 

 found associated together at the Cordova and Deloro mines in Hastings 

 County. Dr. Miller describes these occurrences as follows: 



^Cordova Gold Mine. "The ore-bodies occur in a coarse-grained 

 gabbro-diabase which invades the Grenville and Hastings series. The 

 veins are of quartz, with which are associated iron pyrites, feldspar 

 and calcite. The wall rock has been altered to a chlorite-schist, or 

 chlorite-mica schist, sometimes 50 feet wide, there being a gradual 

 transition between the fresh gabbro-diabase and the schist. The 

 latter is impregnated with quartz veinlets, parallel to the schistosity. 

 Consequently there is not a definite boundary line between the ore 

 and the schistose wall rock." 



"The deposits may have been formed by hot solutions which fol- 

 lowed the intrusion of the gabbro-diabase." 



"The coarse-grained rock at the Cordova gold mine, has sometimes 

 the texture of a diabase and sometimes that of a gabbro, one facies 

 passing gradually into the other. It has been, therefore, called the 

 Belmont gabbro-diabase, the word "Belmont" referring to the lake 



1 Willet G. Miller and Cyril W. Knight. The Pre-Cambrian Geology of South- 

 eastern Ontario. 22nd Rep. Ont. Bur. Min. Part II, 1914. pp. 110 and 31. 



