ANIMIKIE ROCKS OF THE MESABI IRON RANGE. 383 
‘Chester, I have a full collection of rocks from this place. He describes the 
Mesabi Range proper as a backbone of red granite, south of which occur 
the Animikie slates, which are here nearly horizontal, dipping 2° or 3° to 
the southeast. The exposures are large, presenting often a bold cliff side 
of nearly horizontal layers, and have been traced by Professor Chester a 
distance of some six miles along the strike, in the southwest part of T. 60, 
R. 12 W., and the southeast part of T. 60, R. 13 W. The principal rock 
is an arenaceous gray quartzite or quartz-slate, impregnated with magnetite, 
which is often aggregated into bands of some richness. The specimens 
kindly given me by Professor Chester are indistinguishable from much of 
the magnetitic quartzite of the Penokee Range of Wisconsin! — - 
Professor Chester writes me with regard to these rocks: 
On the south side of this range [the Mesabi Granite Range] magnetic iron is 
found in abundance, particularly in T. 60, R. 12 W. and 13 W. Here the ore body 
ds of some magnitude, sufficient to induce a considerable exploration in this part, but 
no large bodies of ore have been found of sufficient value to warrant developments. 
The ore is magnetite, quite similar to that of the Penokee Range. It lies in nearly 
horizontal beds, interstratified with quartzite, so as to make it quite impossible to sort 
out any quantity of good ore. In places where it is exposed on the surface for some 
distance, smoothed and polished by glacial action, at first glance it would be con- 
sidered valuable, but closer inspection shows that it is mixed with rock so as to have 
a Striped appearance. This is particularly noticeable in the sides of the pits sunk down 
init. A layer that shows the best ore on one side of the pit is white quartzite on the 
other. The layers of good ore are thin, about six inches being the thickest found that 
showed good ore ail across, and would average 60 per cent. of iron. <A cliff in See. 
17, T. 60, R. 12 W., shows as follows, beginning at top: Ore of about 50 per cent., 
2 inches; ore with some bands of 60 per cent., 1 foot 6 inches; ore much mixed with 
quartzite, 2 feet 6 inches; ore about 58 per cent., 2 inches; ore and quartzite poorer 
‘than above, 10 feet S inches; quartzite with very little ore, 10 feet. A great many 
such sections were examined, and about two feet of ore was the thickest layer found. 
The rocks are quartzites and slates, more or less altered. They lie more nearly hori- 
zontally than any other beds I have ever examined, changing dip very slightly from 
point to point, giving the idea of a sort of undulating surface, yet, on the whole, dip- 
ping slightly to the south. 
This description, save as to the horizontality, would do as well for 
hundreds of exposures on the Penokee Range of Wisconsin. 
Still farther southwest from here the same magnetitic rocks are exposed 
-on the Mississippi River at Pokegoma Falls in the eastern part of T. 55 
1See Geology of Wisconsin, Vol. III, pp. 118-136. 
