224 TJie American Geologist April, i89s 
feldspars between Moose and Snowbank lakes, and at Zeta 
lake. 
3. Granitic intrusion. This intrusion is frequently char- 
acterized by fine-grained granites or felsytes, but is chiefly rep- 
resented by the granite of Saganaga lake, which is frequently 
very coarse. The Upper Keewatin lies unconformably upon 
it at Saganaga lake, with a profound erosion interval between, 
but this granite cuts older greenstones and green schists (No. 
4) at West Seagull lake. Such granite is seen at Ely (a little 
west of the village) in the form of a light-colored felsitic dike 
or quartz porphyry, which can be traced for a quarter of a 
mile east and west. It also occurs on the Kawishiwi river. It 
supplied numerous bovilders for the conglomerates seen in the 
Upper Keewatin. 
4. The Kawishizvin or Lower Keewatin. This is the old- 
est known formation in the state,* and is essentially a green- 
stone formation, in which the rock is both massive and frag- 
mental. When stratified, as it is over large areas, it consists 
of basic tuffs, agglomerates and green, stratified schists and 
greenwackes. It contains the banded jaspilytes and iron ores 
at Vermilion lake. At Moose lake is a jaspilyte iron ore 
which is at the same time a coarse conglomerate, but it is not 
certain that this is in the Lower Keewatin. These green- 
stones, with their attendant schists and jaspilytes and green- 
wackes, are cut extensively by granite, and by quartz-porphy- 
ries, as above mentioned, and are converted to mica schist 
and banded gneiss, and in that form are very widely extended. 
There is frequently considerable doubt whether some of the 
Minnesota areas of gneiss and mica schist (Coutchiching?) 
belong to the Upper or to the Lower Keewatin. 
No account is here taken of the diabase dikes, whether 
Keweenawan or earlier, which are not uncommon. 
Unconformably above all these is the Animikie formation, 
ot the age of the Taconk, the base of the Paleozoic. This 
formation is tilted but not closely folded. It contains the 
iron ores of the Mesabi range, as well as those of the Peiiokee 
and, when broken and overwhelmed by the Norian, it wit- 
nessed another, but less extensive, granitic intrusion. 
*In a former scheme of the structure of the Archean this was jMit at 
the top of the Keewatin (20th report, p. 4.) but later field observations- 
have shown it is the oldest known rock terrane of the state. 
