OF CENTRAL CANADA PART V. 



337 



of Buckingham, Templeton, Lochaber, and Grenville, on the Ottawa,* 

 and throughout that section of country, generally. About 20,000 

 tons were obtained from these deposits in 1886, and they are still 

 being largely worked. Veins and large lenticular masses of graphite 

 occur also in the rocks of this district, and mica of good quality has 

 been obtained from localities in Grenville, Templeton, and adjacent 

 townships. Iron ore in workable quantity occurs also in Hull, and 

 elsewhere in the same district. 



The orthoclase gneiss- rocks which form the prevailing strata of 

 this archeean region north of the St. Lawrence, are overlaid in some 

 few localities by comparatively limited areas of feldspathic rock com- 

 posed of labradorite or other triclinic lime-feldspars ; and here and 

 there these labradoritic rocks or " anorthosites," see page 181, are 

 apparently interstratified with the upper beds of the ordinary otho- 

 clase gneisses. They were at one time, and are still by some 

 observers, regarded as indicating a newer or higher series of Lauren- 

 tian strata, and were known as the Upper Laurentian, Labrador, or 

 Norian formation, But in the main mass of these anorthosites there 

 is no apparaiit stratification, and they are now regarded by Dr. 

 Selwyn as essentially eruptive rocks of Laurentian age. This view, 

 although not absolutely free from doubt, will probably meet with 

 general acceptance. A large area of these anorthosic rocks occurs 

 in the counties of Argenteuil, Terrebonne, Montcalm, and Joliette ; 

 and another, equally large, lies around the north-east and south sides 

 of Lake St. John, at the head of the Saguenay River. Smaller areas 

 O3cur on the north shore of the St. Lawrence in Montmorenci and 

 Charlevoix, and a large exposure has been recognised on the branches 

 of the river Moisie, off the Gulf. These feldspathic rocks present 

 generally light shades of colour, and weather dull white. In most 

 examples, some of the cleavage planes shew a blue or green opales- 

 cent play of colour, as in typical examples of labradorite ; and 

 occasionally, as at Chateau Richer and elsewhere, they contain scales 

 and folise of bronze-coloured or green hypersthene or bronzite. Gai- 

 nets, also, are frequently present in them ; and they are associated in 

 many localities with titaniferous iron ore. A very large deposit of 

 the latter mineral occurs in these rocks near Baie St. Paul ; and 



* The distinctive characters etc. , of this valuable mineral (known commercially as "phos- 

 phate") are given on page 135. 



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