Mr. T. S. Hunt's Examinations of some Felspathic Rocks. 355 



graphite, and other characteristic minerals. Associated with 

 these limestones, there is another rock forming an important 

 member of the group, and consisting chiefly of felspar, with 

 small portions of black mica, green pyroxene, and occasional 

 grains of garnet, epidote, and more rarely of quartz. This rock 

 is often marked by the presence of small portions of hypersthene ; 

 from the presence of this mineral, these masses havebeen described 

 by the New \ork geologists as hypersthene rock. In addition 

 to these minerals we may add ilmenite, or titaniferous iron ore, 

 which occurs sometimes in large masses, and at other times in 

 small disseminated grains, which like the hypersthene appear to 

 mark the planes of stratification. If to these we add small por- 

 tions of iron pyrites and a little disseminated carbonate of lime, 

 we have the mineralogy of the rock so far as yet known. 



The texture of these felspar rocks is varied; sometimes the 

 mass is a confusedly crystalline aggregate, exhibiting cleavage 

 surfaces three or four lines in diameter, with a fine-grained, 

 somewhat calcareous paste in the interstices. Sometimes the 

 whole rock is uniformly granular, while more frequently a gra- 

 nular base holds at intervals cleavable masses of felspar, often 

 several inches in diameter. The colours of these rocks vary from 

 grayish and bluish-white to lavender and violet -blue; flesh-red, 

 greenish and brownish tints are also met with ; the colours are 

 rarely brilliant. These felspars seldom occur in distinct crystals, 

 but their cleavage is triclinic, a fact which, coupled with their 

 densities varying from 2*66 to 2*73, shows them to belong to 

 the group of which albite and anorthite may be taken as the 

 representatives. The bluish cleavable varieties often exhibit the 

 opalescence of labradorite, to which species American mineralo- 

 gists have hitherto referred them ; but with the exception of a 

 few analyses by myself, we have no published analyses of any of 

 these felspars. My investigations show, that while all of them 

 are felspars with a base of lime and soda, the composition varies 

 very much, being sometimes that of labradorite, andesine or in- 

 termediate varieties, and at other times approaching to that of 

 anorthite. The results of these examinations, as far as yet com- 

 pleted, I propose to give in the present paper, as the first part 

 of the history of these felspathic rocks. 



One of the most interesting localities of these felspars is in the 

 parish of Chateau Kicher, in the county of Montmorenci near 

 Quebec, where they cover a breadth of two or three miles across 

 the strike, bounded by crystalline limestone on one side, and a 

 quartzo-felspathic rock on the other, and rising into small hills. 

 In this region several varieties of the rock appear, but the most 

 interesting is made up of a finely granular base, greenish or 

 grayish -white in colour, holding masses of a reddish cleavable 



2 A2 



