[ADAMS 4 BARLOW] ALKALI SYENITES OF EASTERN ONTARIO 56 



The amount of pyrite is calculated by assuming that the excess of 

 ferric iron over the amount required to form magnetite with the fer- 

 rous oxide, is united with sulphur. 



The position of this rock in the Quantitative Classification is as 

 follows : — 



Class I Persalane. 



Order 4 Britannare. 



Sub-rang 4 Kallerudose. 



Sub-rang 4 Kallerudose. 



(near Xordmarkase). 



If, however, the calcite be regarded as secondary and its lime be 

 calculated as anorthite, on the supposition that it was really present in 

 the original magma while the carbonate acid was not, this increase of 

 salic lime will be just sufficient to carry the rock over into Order 5, 

 and thus make it a Canadare with the sub-rang Nordmarkose. Mineralo- 

 gically it differs from the white syenite just described in containing no 

 nepheline or muscovite, but in holding a little quartz. The mode of 

 this rock is nearly normative — that is, the actual mineral composition 

 is nearly that set forth in the norm. The hypersthene of the norm 

 belongs to the biotite of the rock, the former mineral not being actually 

 present. The calculation shows that there is really relatively more al- 

 bite present in proportion to' the orthoclase than would be supposed from 

 a study of the thin sections. It also shows that there is rather more 

 quartz present than would be expected from an examination of the hand 

 specimens or the slides, and also that the rock must contain some free 

 alumina in the form of corundum, although this mineral does not hap- 

 pen to occur in any of the thin sections of the rock from this particular 

 locality, which have been prepared. As has been mentioned, however, 

 corundum is found abundantly in the veins or dykes of syenite peg- 

 matite which cut the rock at this locality. The occurrence of free 

 quartz and corundum in the same igneous rock appears to be an anomaly. 

 If, however, the quartz be secondary, the anomaly disappears. 



Where this reddish syenite, a mile and a quarter to the south-west 

 of the locality just described, crosses the road running from Lake Kasha- 

 bog to Jack's Lake, on lot 6, con. XII of the township of Burleigh, 

 it in places holds corundum in large amount. Under the microscope 

 the rockj is seen to consist of albite, microcline, orthoclase, biotite, mus- 

 covite and corundum. The albite preponderates largely in amount over 

 the potash feldspars. Biotite is present only in very small amount, but 

 there is a considerable percentage of muscovite in irregular-shaped in- 

 dividuals which have a tendency to a lath-shaped development and which, 

 if they occur in groups, frequently penetrate one another and also pene- 



