OF CENTRAL CANADA PART III. 187 



less perceptible, individually. Fine-grained varieties, which offer a 

 transition into basalt proper, have been classed apart, by some litholo- 

 gists, under the name of Anamesite. In these, the component minerals 

 are scarcely, if at. all, observable. Dolerites, as a general rule, are 

 chiefly of a greyish colour, varying from light-grey with black specks 

 and indistinct crystals of augite, to an almost uniform black or dark- 

 grey tint. When much olivine is present, and occasionally in other 

 cases, the rock assumes a greenish-grey or brownish-green colour ; 

 and weathered examples are frequently rusty-red, or otherwise dull 

 white. Sp. gr. =2.7. 3.0. 



This granitoid condition of trap presents, as in ordinary basalt,, 

 massive, slaty, columnar, amygdaloidal, and porphyritic varieties. 

 Examples occur generally throughout Canadian districts in which 

 trappean rocks prevail ; especially in the Townships of Grenville, 

 Chatham and Wentworth in the Ottawa region ; also in parts of the 

 Montreal Mountain and in the mountains of Montarville and Rouge- 

 mont, and other parts of that district ; abundantly also on the shores 

 and islands of Lake Superior, (G-ros Cap, Goulais Bay, Montreal 

 River, &c.,) and throughout the northern lake region generally. 

 The dyke on Slate River, shown in figure 102, consists of grey 

 dolerite. 



Greenstone or Aphanite is a compact trappean rock of a more or 

 less decided green colour, passing into greenish-black. It is assumed 

 from its general composition to be made up of an intimate mixture of 

 lime and soda feldspars and hornblende, with very generally a certain 

 amount of magnetic and titaniferous iron ore, and some carbonate of 

 lime. Strictly, it cannot be distinguished, except conventionally by its 

 green colour, from ordinary trap. It presents massive, slaty, 

 columnar, anygdaloidal, and pophyritic varieties, and passes into 

 diorite and diabase, the latter by the addition of chlorite, as well as 

 into common trap. Dykes of this green variety of trap occur here 

 and there on Lake Superior, but most of the so-called greenstones of 

 that region are evidently chloritic, and hence would be regarded by 

 systematists as compact and amygdaloidal varieties of diabase. Dykes 

 of somewhat similar character occur also in the Madoc and Marmora 

 region, and undoubtedly in other districts. The terms Greenstone 

 and Aphanite, it should be observed, are applied by some authors to- 



