Ifi4 THE PENOKEE IRON BEARING SERIES. 



From the section at the Mount Hope mine. 



27. Ferruginous quartzite, from the uppermost layers, being the foot wall at 

 the Mount Hope mine. Specimen 7611 (slide 2307). From 1140 N., W., Sec. 23, T. 

 47 N., R. 47 W., Michigan. 



The thin section is composed of large interlocking quartz areas, at the junctions 

 of which arc often films of brown iron oxide. Each ijuartz area is furnished with a 

 very distinct, well rounded, fragmeutal core. 



From the xcction, between the Bhie Jdckct and First Ndfiotuil mines. 



28. Cherty quartzite, from a low horizou. Specimen 7002 (slide 2010). From 

 1900 N., 1150 W., Sec. 1!), T. 47 N., R. 46 W., Michigan. 



Both in the hand specimen and in the thin section this rock is like 23, which 

 occurs at a similar horizon. 



29. Ferruginous (juartzite, from a middle horizon. Specimen 7603 (slide 2303). 

 From 1980 N., 900 W., Sec. 19, T. 47 N., R. 46 W., Michigan. 



The specimen and thin section are as in 27. 



From the Colby mine section. 



■W. Sericitic and chloritic slate (novaculite), from a low horizon. Specimen 

 9.523 (slide 3(»91). From 77.5 N., 770 W., Sec. 16, T. 47 N., R. 46 W., Michigan. 



This rock in specimen and tliiii section resend)les closely 9038 and 9044 in IS, 

 from the West branch of the Montreal river. (PI. xviit, Fig. 4.) 



31. (v'liartzite, from a high hoiizon. Specimen 7591 (slide 2006). From 1(»00 

 N , 548 W., Sec. 16, T. 47 N., R. 46 W., Michigan. 



This rock in specimen and thin section is lik^e 7620 in 24 from the Ashland 

 mine section. 



From the Tilden mine section. 



32. Quartzite, from an upper horizon. Specimen 12524 (slide 5333). From 1228 

 N. to 1153 N., 1166 W., Sec. 15, T. 47 N., R. 46 W., Michigan. 



The rock is a line grained, massive, greenish giay Vitreous quartzite, having a 

 conchoidal fracture. 



The thin section consists chiefly,of rather small interlocking (piartz areas, each 

 with its fragmeutal core. A considerable (luantity of fragMicntal feldspar is also 

 present. Outlining the original fragments of quartz are lilms of chlorite and ferrite, 

 the green i si I color of the rock being produced by the former. The chlorite and fer- 

 rite particles also occur where the enlargements of the difl'erent grains meet each 



other. 



From the r<(lms mine section. 



33. Conglomerate. Specimens 12522 (slide 5388), 12893 (slide 5511). From 

 SE. i of NE. i. Sec. 15, T. 47 N., R. 46 W., Michigan. 



