HARRINGTON — CANADIAN MINERALS. 



255 



No. 4.] 



it shows a more or less banded structure. As observed above, an 

 enstatite-like mineral may occasionally be seen in the hand 

 specimen, but none of it happened to occur in the portion sliced. 



Fig. 1. 



^ Fig. 1 h is dr.iwn from a section of one of the so-calied serpen- 

 tines occurrino' near the dunite. Its relation to the latter is 

 evident, for it still contains numerous grains of unaltered olivine. 

 In some specimens the change has not advanced so far as here, 

 but in other eases the olivine has almost, if not entirely, disap- 

 peared. The chiomite, however, always remains. 



Another example of the occurrence of olivine is to be found in 

 the case of a dark grey dolerite occurring near South Lake, in 

 Antigonish County, Nova Scotia. When a section of the rock 

 IS examined with the microscope, it is seen to consist of a beau- 

 tifully banded triclinic feldspar, brownish augite, magnetite, and 

 very numerous irregular grains, or occasionally rude crystals, of 

 ohvme. The olivine resembles that sometimes seen in gabbro. 

 It is traversed by the usual cracks or rifts, which in this case 

 appear very broad and black, and also contains great quantities 

 of black and opaque microlites, which are probably magnetite, 

 and which are sometimes so abundant as to render the mineral 

 almost opaque. Some of them are arranged in parallel rod-like 

 shapes, while others occasionally assume star-like or other more 

 or less symmetrical Ibrms. 



Olivine has also been detected in several of the eruptive rocks 

 of British Columbia. One of these, of Tertiary age, from Kam- 

 loops, affords most beautiful examples of the alteration of olivine 

 to serpentine. It is massive, rather fine-grained, and of a very 

 dark olive-green colour. The examination of a slide with the 

 microscope shows that originally the rock must have consisted of 



