GEOLOGICAL EXPLORATIONS AND LITERATURE. 55 



Rctuniiiij; now to Ko. VIII of our cross section wc find it and No. X repre- 

 sented by actinolo iiiaguetic scliists. These members are more or less magnetic, 

 depending- on the jjerceutage of magnetite and otlier conditions. . . . 



The magnetic schist is ))anded, with layers of lean ore impregnated by actiuo- 

 lite; also layers of arenaceous quartz and occasionally a thin one of magnetic ore. 

 The l>ands vary in thickness from a mere line to one or more inches. Some portions 

 of it are quite slaty aiid jointed. The texture on a fracture is usually fine grained. 

 The color varies from gray to brownish black. . . . 



Xo. XII, usually represented in the Marquette iron district by a lianded Jasper, 

 which forms the "foot wall" of the iron ore, we did not find outcropping west of the 

 Penokee gap, but since we were on the range I have been shown by exploring parties 

 several samples of jasper and specular and magnetic ore (probably No. XIII) which 

 they found east of the Gap. . . . 



No. XIV. I have also seen specimens of gray quartzite fi-om east of the Gap, 

 which were very similar to that forming the hanging wall of the Marquette iron ore 

 mines, and for this reason we will for the present refer it to No. XIV. The next num- 

 ber in tlie regular order, Xo. XV, a micaceous argillite or slate is found outcropping 

 in Sees. 9, 10, and 11, T. 44, R. .3 W. The outcrops were small and formed at 

 most only low, narrow ridges, which is no doubt due to the perishable nature of the 

 rock. In many respects it resembles the argillites described under Nos. VII and IX. 



The rock is dark brownish l)lack, has a dull, slaty texture, is strongly jointed, 

 cleaves into imperfect slates, tlie thicker ones having a conchoidal fracture. Examined 

 on a fresh fracture the surface apiiears thickly sprinkled with very minute, shiny 

 scales. . . . 



Xos. XVI to XIX. Within these numbers are embraced a large gi'ou)) of mica- 

 ceous quartz-schists, micaceoiis slates and schists, and chiastolite schist. 



These, with No. XV, no doubt could consistently be comprised under one head, 

 but in order to reach No. XIX, whicli corresponds very nearly with the chiastolite 

 schist of the Michigan series, we will, for the present, retain the numbers without 

 attempting to classify the different .schists. 



The most important member of these is the micaceous quartz-schist. It has an 

 immense development immediately west of the Gap. It is of a dark iron-gray color, 

 and has a very even, fine grained texture. It weathers to a light drab. Under the 

 lens the dark colored mica is plainly ^'isible. Some of the exposed surfaces are 

 minutely pitted, owing apparently to the ])artial decomposition and washing out of 

 the mica. In hand specimens the structure appears massive, but uncovering the 

 ledge the fresh surface frequently shows a slightly banded structure. . . . 



This comjirises all of tlie rocks which I am satisfied belong to the Iron series. 

 Overlying these, apparently nonconformably, are diorites, uralites, diabases, hy^jers- 

 thene, and granitoid rocks. The diabases are massive and fine to very coarse grained. 



