910 A. P. COLEMAN 



I II III 



K2O ----- 0.18 1.06 2.44 



C02 ----- 1.03 (HoO) 0.55 .... 



101.35 100.49 100.70 



Sp. Gr. 2.85 2.69 2.65 



The low percentage of silica and soda, and the high percent- 

 age of lime as compared with the anorthosite from Quebec are 

 notable and correspond to the results of microscopic examina- 

 tion, the specimen from Seine River consisting chiefly of 

 anorthite, and that from Rawdon of labradorite. The specific 

 gravity, 2.85, is very high, perhaps because of the presence of 

 considerable zoisite. The specific gravity of a specimen from 

 Bad Vermilion Lake was determined to be 2.76, corresponding to 

 its slightly more acid character, since it consists of bytownite. 



The results of the analysis show that the anorthosite from the 

 mouth of the Seine is one of the most basic of the massive rocks, 

 having about 8 per cent, less silica than the typical rocks of 

 eastern Canada, but it is probably wiser to include it among the 

 anorthosites, since the somewhat more acid rock from Bad 

 Vermilion Lake links it to the eastern ones. 



It would perhaps be most logical to name the whole series of 

 rocks consisting essentially of plagioclase anorthosites or plagio- 

 clasites,^ adopting a binomial nomenclature like that tacitly 

 admitted in the classification of other rocks, such as the granites. 

 We should then speak of anorthite, bytownite, and labradorite 

 anorthosites or plagioclasites ; and the list might require to be 

 extended to include andesine and oligoclase rocks, perhaps also 

 albite rocks. The albitites described by Turner from California, 

 under the head of syenites, are dike rocks apparently and 

 should perhaps not be classed with the plutonic rocks referred 

 to here.^ The name anorthosite has priority but has a very 

 tautological sound in the term describing the rock just discussed, 

 anorthite anorthosite. 



Lawson looks on the anorthosite and granite areas of Bad 



' See Viola as quoted by Rosenbusch in Massige Gesteine, Erste Halfte, p. 298. 

 'American Geologist, June 1896, p. 379, etc. 



