75 



other decomposition products are present. Under the mic- 

 roscope certain thin sections of the greywacke resemble 

 volcanic ash. It has not been proved, however, that there 

 was contemporaneous volcanic activity. 



Typically, the slate-like greywacke has a greenish or 

 greyish color, but in certain localities the color of the rock 

 is distinctly reddish. The latter color is not found in the 

 greywacke of the productive part of the Cobalt area proper, 

 but reddish greywacke lies both to the west and to the east, 

 outcropping in the western half of Coleman township, near 

 Latchford on the Montreal river, and at two or three points 

 near the shores of lake Temiskaming. 



The greywacke, like the other members of the Cobalt 

 series, lies usually in an almost horizontal position. Ripple 

 or wave marks are frequently seen on the surface of its 

 beds, e.g., in the cliff at the Little Silver mine on the 

 Nipissing property. Mud cracks have also been observed. 

 While usually showing little evidence of disturbance, the 

 greywacke is quite compact and does not split readily along 

 the junction of many of the beds. 



Normally, the greywacke passes upwards into quartzite, 

 more or less impure, and the latter into conglomerate, but at 

 times the quartzite is lacking and the greywacke is suc- 

 ceeded by conglomerate. Where the members of the series 

 are complete, as at some points along the eastern shores of 

 lake Temiskaming, the conglomerate appears to be suc- 

 ceeded without unconformity by what has been called the 

 Lorrain arkose and quartzite, the latter of which is fre- 

 quently interbanded with pebbly material. 



At two or three places, however, where the upper 

 members of the series, conglomerate or arkose, lie directly 

 on the greywacke, without the quartzite or other inter- 

 mediate member being present, the greywacke is seen to 

 have been eroded before the deposition of the overlying 

 rock. 



Quartzite. 



The quartzite usually has no great thickness, frequentlv 

 being only twenty or thirty feet, but in certain localities 

 impure quartzite or greywacke that overlies the delicately 



