Hornhlende Lamiwopliyre Dyke at Riclimond, P.Q. 317 



A greenish substance, nearly or quite isotropic, which is 

 associated with calcite in places, and commonly forms 

 pseudomorphs after hornblende, is regarded as chlorite. 

 In association with calcite it occasionally shows aggregate 

 polarization and sometimes has a more serpentine-like 

 appearance, where it probably consists in part of that 

 mineral. 



The iron ore is in black angular grains, which have a 

 metallic lustre and are all thought to be primary. Its 

 general characters are those of magnetite, some of the 

 larger grains containing cores of leucoxene, thus indicating 

 its titaniferous nature. 



Needles of apatite penetrate both feldspar and horn- 

 blende. 



The rock thus belongs to the dark-colored trap dykes, 

 or lamprophyres, and agrees most closely with the 

 characters of Camptonite, of which it is a fairly typical 

 specimen. 



The known occurrences of Camptonite in eastern ISTorth 

 America include Montreal and the shores of Lake Mem- 

 phremagog in Canada, as well as several localities in the 

 states of New Hampshire and Vermont, southern Maine 

 and eastern New York.^ The nearest of these, that at 

 Lake Memphremagog, is about fifty miles south of the 

 present occurrence. 



Camptonite is commonly, though not invariably,^ ail 

 accompaniment of highly alkaline rocks, such as nepheline 

 syenites, no occurrence of which is known, however, 

 nearer than Brome and Yamaska mountains, some fifty 

 miles to the westward. From the presence of such dykes 



1 " The Trap Dykes of the Lake Chaini)laiii Region," by J. F. Keinp and V. F. 

 MarstPi-s. Bull. U.S. G.S., No. 107. " Camptonites and othei- Intrusives at Lake 

 Meniplireniasog," by V. F. Marsters. Amer. Geologist, July, 1895. 



2 "Geology of the Castle Mountain Mining District." Weed and Pirsson. Bulletin 

 U.S. Geol. Survey, No. ia9, p. 111. The authors here Cite Br'ogger'.s opinion, deduced 

 from the study of the basic rocks of Gran, Norway (Q. J. G. Soc. London, Feb., ]S94), 

 that Camptonite is "not necessarily indicative of the presence of a definite type of 

 granular pUitonic rock as formerly supposed." 



