T. B. Brooks— Rocks observed in the Huronian Series. 201 
and to add limonites, which are so closely renee to the others 
that it was not attempted to separate them her 
Tron-oxide, except as disseminated grains of magnetite and 
in a few instances in small unworkable beds, is entirely absent 
from the Laurentian and Copper-bearing series of the Archean 
south of Lake Superior, while in Canada the largest deposits are 
reported as occurring in the Laurentian. Titaniferous iron-ore, 
80 eaaiiant| in the Rhean of Canada and nathan. New York, 
(A.) Magnetites ‘ane Magnetic Quartzose and Amphibolic Rocks. 
Most abundant and, except the amphibolic kinds, found only 
in typical forms in the western part of the Maxquette Region. 
a. Rich in iron (tron-ores). 
al. Blackish granular magnetites, massive to semi-schistose, 
fine to coarse grained, compact to friable—89, 40, 41, 
a2. Cryptocrystalline, eon pars, tabular, schistose, ‘sometimes 
containing actinolite—17 ? 
b. Poor in iron, rich in quarta, (magnetic pigs bes! iepaer es 
in the Marquette Region, especially in the western part ; 
abundant in the Penokie (Bad River) series. 
bl. Banded, arenaceous quartz and magnetite layers—52. 
2, Intimate mixtures of magnetite (with heisaeites ae quartz- 
ose matter, often cherty. Magnetic siliceous schist (flag ore)— 
28,15. Both varieties graduate into ferruginous quartzytes. 
© Ferruginous rocks, rich in amphibole,—the iron-oxide mostly 
magnetic. (Here are embraced such anthophyllite schists as are 
rich in iron.) Tolerably abundant in the Menominee Region 
el. Banded quartzose, amphibolic (mostly anthophyllitic, 
according to Brush), magnetic schists—130, 17. According to 
sa ja chmann the iron-ore at Penokie Gap i is a related variety 
i ne Man ne 41 5 Miceieg fod he en Galt ists—5 & Onl 
in western p part of the Marquette Region, constituting bed X 
¢3. Garnetiferous anthophyllitic magnetite schist (eklogyte) 
~27, Only in one bed in the Marquette Region. 
se) lar Hematites, Martites, and siliceous, jaspery, @ u- 
ematitic rocks. Most abundant and typical in the east- 
ern a of the Menominee Region. 
a. Rich in iron. 
vg Granular, massive to semi-schistose, specular hematite 
Pm martite. Usually contain a little magnetite. Not so 
ndant as the magnetites of corresponding structure—d. 
* See my Michigan Report, vol. i, chap. x, 1873. 
