PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 807 



Zirkelyte. Diabase. Conglomerate.) 



No. 1899. ZIRKELYTE. 



At the west side of the outlet of South Fowl lake, from the hill at the creek. 

 Ref. Annual Report, xxii, page 12. 



Meg. From the margin of the conspicuous dike which cuts vertically the trap hill. 



Mic. The section consists largely of devitrified magma glass. But, arranged in 

 a divergent manner, are fine, elongated crystals of a feldspar and of a composite 

 element, which, according to its extinction angles, consists of hornblende and pyroxene. 

 These fine elongated crystals, when viewed with high power, have two angles of 

 extinction, viz., the central portion, which is somewhat dimmed by decay, at 5 to 

 10, and the peripheral portion, which is fresh, at about 45. The elongation and 

 general habit are amphibolic, and it may be supposed that after the formation of 

 the hornblendes, which was about coternporary with that of the feldspars (as they 

 mutually cut each other), a change in the environment and in the composition of 

 the magma caused a zone of pyroxene to envelop them. On the other hand the 

 hornblendic cores may be due to alteration of original pyroxene. One section. 



Age. Manitou(?) N. H. w. 



No. 1900. DIABASE. 



Same place as the last. 



Ref. Annual Report, xxii, page 12. 



Sample representing the rock of the hill, remote from the dike. 



Mic. The ophitic structure is evident in some parts, but at the same time some 

 of the feldspars were later than the final crystallization of the auyite, for they are 

 broken about their margins by the augite. There is no visible olivine, probably 

 because of alteration by weathering, which is apparent in all the minerals. One section. 



Age. Cabotian(?) 



Remark. This is called diabase, because of the ophitic structure, but it is 

 supposed to be a portion of the great gabbro mass of the Cabotian, which frequently 

 does not show the ophitic structure. N. H. w. 



No. 1901. DIABASE. 



Same place as the last. 



Ref. Annual Report, xxii, page 12. 



Sample of the rock of the cliff near the dike. 

 Mic. This rock is much finer grained than No. 1900, but is not essentially 

 different. It is likewise much weathered. One section. 



Aye. Cabotian. N. H. w. 



No. 1902. CONGLOMERATE. (Quartwsc.) 



Valley of the Puckwunge, about at the centre of the N. W. ^ sec. 25, T. 64-4 E. 

 Ref. Annual Report, xxii, page 12. Compare No. 2069. 



Mey. Rather fine, quartzose, but containing some colored pebbles and grains. 



