PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 597 



Conglomerate. Pebbles. Jaspilyte.] 



siderite rather than calcite is shown by its frequently marked absorption, stronger 

 than calcite commonly shows, and by the fact that the powdered rock effervesces 

 very freely in hot hydrochloric acid, while there is almost no effervescence in the 

 cold acid. 



One section. 



Age. Keewatin. u. s. G. 



No. 908. CONGLOMERATE. 



North of the Cady house on the South ridge, Tower. 



Ref. Annual Report, xv, pages 268, 269, 389; Annual Report, xvii, pages 194, 215. 



Meg. A fine-grained, gray, schistose rock which contains small grains of 

 feldspar, some of quartz and rock fragments. One of the specimens contains a piece 

 of a black, hard, slaty rock. The rock is a rusty weathering one. On fresh fractures 

 very minute, silvery, micaceous scales are abundant. 



Mic. Angular grains of feldspar and quartz are embedded in a finer-grained 

 groundmass, but there are all variations in size between the feldspars and quartzes 

 visible in the hand sample and the minute ones of the groundmass. The rock is 

 schistose and the groundmass is composed essentially of quartz, feldspar, muscovite, 

 chlorite, calcite, dust-like black material, and probably also kaolinite. One of the 

 slides shows a fragment of a black rock which consists of a few scattered, lath- 

 shaped feldspars, in a confused dark background. 



Two sections. 



Age. Upper Keewatin. u. s. G. 



No. 908 A. PEBBLES (from No. 908). 



Same locality as No. 908. 



Ref. Annual Report, xv, page 389. 



Meg. There are four of the pebbles, or rather fragments of pebbles. One 

 is a fine-grained, granular, somewhat crumbling, white quartzyte or jaspilyte. 

 Another is a fine-grained, hard, black, slaty rock. Another is a very fine-grained, 

 gray rock, with a few small grains of quartz. Another is fine grained, greenish 

 gray and somewhat porous. Another is fine-grained, hard, almost flint greenstone. 

 Another is black, slaty jaspilyte. 



Mic. The section was evidently made from the first-mentioned pebble, which 

 is seen to be an almost pure, completely crystallized, fine-grained quartzyte, or a 

 rather coarse-grained jaspilyte. One section. 



Age. Pebbles in Upper Keewatin rock. u. s. G. 



No. 909. JASPILYTE. 



A little north of, but near, Tower. 



Ref. Annual Report, xv, pages 229, 268, 389. This rock is embraced in a clastic green schist similar to 

 No. 910. 



