THE QUARTZ-SLATE MEMBER. 



169 



From llie section in northern part of Sec. 14, T. 47 K, R. tr, W., Michigan. 



4!t. Chert-conglomerate, from the bottom of the Quartz-slate member. Speci- 

 mens y^lS (slide 30.59), 9419 (slides 312G, and 3127), from 1775 N., 1075 W., See. U, T. 

 47 N., R. 45 W., Michigan. 



The matrix of this conglomerate is fine grained and of a dark green color. In 

 the matrix are buried very plentiful rounded fragments of transhu'cnt opaline chert, 

 which vary in size from three-fourths of an inch to two inches in diameter. 



The matrix of this conglomerate is seen in the thin section to be composed of 

 ra^^ther small fragments of (|iKutz and feldspar, the former predominating, mingled 

 with a considerable proportion of interstitial cherty and amorphous silica, along with 

 some chlorite, brown iron (»re, and kaolin. Large particles of mica, api)arently frag- 

 mental in natiue, are also seen. The pebbles are wholly composed of a chert identical 

 with that of the limestone member below, being in part a minutely crystalline and m 

 part an amoriihous silica. The slides closely resemble 31.34 and 1951 in 40. (PI. 

 XVII, Fig. 3.) 



50. Cheit-l>reccia or conglomerate, from the bottom of the Quartz-slate member. 

 Specimen 941.'0 (slide 30«0), from 1775 N., 1225 W., Sec. 14, T. 47 N., R. 45 W., Mich 

 igan. 



This rock differs from 49 in that its matrix appears to be a chloritic and ferru- 

 ginous chert, while in the latter the matrix is entirely fragmental. 



The pebbles and matrix in thin section differ from each other only in purity; 

 the pebbles being c<mi])osed of a .senncrystalline cherty silica, while the matrix is 

 composed of the same silica mingled with nnicli ferrite and chlorite. A few large 

 fragments of quartz are seen. 



51. Quartzite, from near the bottmn of the Quartz-slate member. Specimen 9421 

 (slide .3001), from 1775 N., 1200 W., Sec. 14, T. 47 N., R. 45 W., Michigan. 



A dark reddish, semivitrecms (|uart>.ite. 



In the thin section well rounded ijuartz fragments with small enlargements are 

 buried in a line interstitial material composed of minutely crystalline and amorphous 

 silica, kaolin, chlorite, and brown iron oxide. 



From the exposures on the Peninsular Mining Company's property. 



52. Ferruginous quartzite. Specimen 12789 (slide 547C), from 1910 N., 1040 W., 

 Sec. 13, T. 47 N., R. 45 W,, Michigan. 



A medium grained, vitreous quartzite, stained a dark brown coloi- by iron oxide. 



About one-half of the thin section is composed of widely enlarged fiagnients of 

 quartz; the main part of the remainder of the section consists of minutely crystalline 

 silica, mingled with chlorite and ferrite particles, with a few fragments of orthoclase, 

 microcliue, and plagioclase. 



