[ami] bibliography OF CANADIAN GEOLOGY 323 



(19) McMillan, James. — " The area is a plain, in all probability once the bed of 



a glacial dammed lake." Rock exposures are uncommon. The greater 

 part of the area has been mapped as Huronian, the most common rocks 

 being variously altered basic eruptives; The regions also includes an 

 area of Laurentian and gneisses. 



(20) Mebbill, F. J. H. — A brief notice of the occurrence of narrow calcite 



veins cutting Grenville limestone and carrying galène, 



(21) Miller, Willet G. — ^" Nepheline syenite in Western Ontario." Am. Geol. 



Vol. 32, pp. 182-185; 1905. 



This article records a probable new occurrence of nepheline syenite 

 in Ontario. The locality is supposed to be near Sturgeon lake, about 

 one hundred and fifty miles northwest of Port Arthur. Boulders have 

 been found and similar rock is supposed to be in a situ near at hand. 

 Hastings County, Kippewa lake, and the Rainy River district have 

 hitherto been the only known localities of the occurrence of this rock. 



The amphibole of the rock has an extinction, C : C, of 20°, which 

 distinguishes it from arfvedsonite. 



(22) Miller, W. G. — The report is accompanied by a map showing the areal 



geology of the district surrounding Cobalt. The oldest rocks are Kee- 

 watin greenstones and schists, these have been intruded by a granite 

 which is classed as Laurentian. Both the Keewatin and Laurentian 

 are unconformably overlain by the Lower Huronian and the latter is 

 separated by an unconformity from the Middle Huronian. The Lower 

 Huronian rocks are conglomerates, greywacke-slates and quartzites. The 

 middle Huronian consists of conglomerates and quartzites. Large areas 

 of diabase are present in the district which are of post-Middle Huronian 

 age and probably occur both as widespread sills and as boss-like bodies. 

 » Tov. îirds the north of the district the above rocks are overlain by beds 



of Silurian limestone. 



The veins of ore are mainly confined to an area 5-6 miles long 

 by 2-3 miles broad. The veins are very narrow and with but few 

 exceptions are confined to the Lower Huronian, but have also been 

 found cutting the Keewatin and the post-Middle Huronian diabase. 

 The veins usually consist chiefly of smaltite, niccolite, calcite and native 

 silver deposited in the order named. These minerals are accompanied 

 by native bismuth argentite chloathite, dyscrasite, etc. The mineral 

 group as a whole is characterized by the subordinate part which sulphur 

 plays in comparison with arsenic. The report contains descriptions 

 amd in ai number of cases analyses of the minerals. The fissures are 

 thought to have been formed as a result of the contraction following 

 the cooling of the diabase and the vein material to have been deposited 

 by heated waters which marked the last phase of the volcanic activity 

 accompanying the intrusion of the diabase. 



(23) Miller, W. G. — ^The iron formation consists of jaspilyte and occurs as a 

 narrow band withiu Keewatin schists, the latter are cut by Laurentian 

 granite and syenite. A few small outcrops of Lower Huronian con- 

 glomerates are present. 



