92 THE MAKQUETTE IRON-BEARING DISTRICT. 



of the SE. \ sec. G, T. 47 N., R. 25 W., Avhere tliey are represented by 

 black slates. From this point tlie formation extends westward, with a few 

 interruptions, to Lake ilichigamme. Sandy micaceous flagstones, black 

 carbonaceous and light slates, and sand-rock, interspersed Avith ferruginous 

 layers, refeiTed to as "flag Ores,'' are all included in the "group." They 

 are the equivalents of the great slate formation at L'Anse and on Huron 

 Bay. All the slates of the series are cleaved, with the cleavage planes 

 usually inclined to the stratification. The sequence of the different members 

 of the formation was not determined, though the lighter-colored layers in 

 the west appear to be tlic upper portion of the series, with the older mendjers 

 farther east. 



Above the "arenaceous slate group" near the railroad, west of the 

 Michigamme mine — 



are outcrops of dark blackisligray rock beds, partly of slate structure, partly iu \vell- 

 lainiiiated, banded, more compact seams, which succession of beds follows immediately 

 above the actinolitic rock series, dijiping in conformity with that southward. These 

 rock beds consist of a subporous groundmass, formed of very minute granules of white 

 translucent quartz, in intermixture with a large proportion of brightly glistening black 

 mica scales, and not rarely also with chlorite. In the softer, quite fissile schistose or 

 slaty beds the mica overbalances the granular quartz, and they have a silky luster. 

 In the compact banded ledges the quartzose groundmass prevails and their aspect is 

 dull. Certain seams inclose an abundance of brown garnet crystals, from the size of 

 a mustard seed to that of a pea. These beds I consider as representatives of the upper 

 horizon of the fifth group ; they correspond with the micaceous schists * * * on 

 the north side of the Keystone mines. * * * On the south shore of the lake, 

 [ Michigamme j opposite Michigamme village, the rock beds come to the surface near 

 the water's edge; we find there silvery-shining gray-colored mica-schists, some .smooth, 

 even bedded, others much corrugated, which essentially (consist of the same minutely 

 granular quartzo.se groundmass mingled with lighter coloied mica scales, which com- 

 poses the schists on the west side of the Michigamme mines. This great similarity iu 

 the sedimentary material is an evidence of the close connection between this mica- 

 schist group and the arenceous slate group, which proves the immediate succession of 

 the iirst to the other more reliably than it is done by the southern dip of the strata, 

 conformable with those of the Michigamme mine. » » * The dip of the nearly 

 vertical rock beds is almost uniformly to the south, but the succession of beds is so 

 immensely large that there must be .suggested a frequent doubling up of the strata, 

 which, in a belt of several miles in width, retain from one end to the other almost the 

 same general rock character." (Pp. 131-132.) 



