PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 747 



Tuff. Conglomerate. Quartzyte.] 



No. 1592. TUFF. (Volcanic.} 



Northwest from the railroad crossing of Vermilion river, Ontario. Prom a ridge that rises from seventy- 

 five to a hundred feet above the railroad. 



Ref. Annual Report, xviii, pages 54, 63. 



Meg. Appears like a " curious conglomerate." 



Mic. In general the slide is nearly dark between crossed nicols, but angular 

 areas, more light than the rest, are more or less sprinkled with small polarizing 

 crystals of various kinds. These angular areas are mainly filled with chloritic sub- 

 stance, which frequently is arranged perpendicularly to the peripheries in fibres, and 

 is also sometimes actinolitic, with high polarization colors. It is also variously 

 irregular, streamed, and in rosettes. Some of the finer angular areas are of quartz, 

 and some are striated feldspar crystals. The matrix which contains these angular 

 areas is at present nearly dark, even in common light, apparently because of spicules 

 and grains of magnetite. One section. 



Age. "Huronian," probably Lower Cambrian. 



Remark. Volcanic products from this region have already been signalized by 

 G. H. Williams (Bulletin of the Geological Society of America, vol. II, pages 138- 

 140). This locality is easily accessible, and the deposit forms a conspicuous hill, 

 or ridge, at the railroad. On the authority of Dr. Robert Bell, who stated that the 

 black slates graduate conformably into this rock, the slates at the Vermilion river 

 (No. 1590) are here made the same age as this volcanic tuff. N. H. w. 



No. 1595. CONGLOMERATE. 



At one and a half miles east of Algoma, Ontario. In the typical Huronian region, by the railroad. 

 Logan's " third slate conglomerate," underlying a gray to black roofing slate. 

 Ref. Annual Report, xviii, pages 55, 63. 



Mey. Conspicuously conglomeratic, but not distinctly bedded. 



Mic. The fine gray matrix consists of clastic materials in which are some fine 

 quartz and some pyroxene, but which is mostly composed of indeterminable and 

 inseparable debris of basic elements (chloritic, leucoxenic and basaltic). In this 

 matrix are angular grains of quartz, of triclinic feldspar, of microcline, sphene and 

 apparently of a devitrified glass or aporhyolyte. These elements were evidently not 

 long exposed to friction of oceanic agitation, if at all, and indeed the whole rock 

 may be of the nature of volcanic tuff, having an origin very similar to that of many 

 pebbly greenstones of the Archean. One section. 



Age. " Huronian." N. H. w. 



No. 1598. QUARTZYTE. ( Feldspathic,. ) 



Pour miles east of Algoma, Ontario, by the railroad. 

 Ref. Annual Report, xviii, pages 55, G3. 



Meg. Fine, reddish. 



