202 T. B. Brooks—Rocks observed in the Huronian Series, 
a2. Chloritic, semi-schistose, specular ores, not abundant, 
a3. Specular-iron schists, often slaty, and passing into mica- 
ceous-iron varieties (the most abundant form of hematite)—88, 
45, 47, 48. 
a4, Micaceous-iron slaty schist; graduates into the last, a8. 
When interstratified with magnetic ore, it usually contains 
magnetite—46, 49. : 
a5. Kaolinic specular schist—2, 44. Rare and observed only 
in the eastern part of the Marquette Region. 
a6. Purplish to pigeon color, shaly to sandy, generally rich 
in iron, dull specular ore—136, 67. Confined to the eastern 
part of the Menominee Region. 
b. Quartzose specular Hematites, poor in iron, poor in quartz. 
Abundant. Graduates into hematitie quartz schist. 
61. Banded, micaceous-iron, quartzose schist—16, 32, 83. 
Abundant in the Marquette Region. 
2. Banded specular-iron with jaspery quartz (‘‘ mixed ore’), 
the laminz often plicated and faulted to the extent sometimes 
of producing a breccia. Abundant with specular ores in the 
eastern part of the Marquette Region— 7. Similar but more 
jaspery and less ferruginous rocks occur in the Black River 
serles—84, 
63. Intimate mixture of specular hematite (often magnetic) 
with quartzose matter, often cherty. Hematitic siliceous schist 
(flag ore). Very abundant—é68, 19, 36. Sometimes contains 
grains, apparently of decomposed garnets (bird's-eye ore)—6. 
c. Hematitic argillaceous, hydro-magnesian and 
schists, sometimes graduating into limonitic varieties, am 
usually associated with rich iron-ore. Poor in iron; generally 
diffused, but not abundant. Included under varieties of clay 
and chloritic slate and mica schist. 
(C.) Limonitic Quartzose Ores and Rocks, often containing hem- 
atite and manganese. Usually some shade of dull brown, ae 
erally soft and more or less earthy. Often contain ochre an 
kaolin (Brush), and probably turgite. Appear to be of the o 
ture of residual deposits, from the partial dissolving out of the 
silica and the hydration of the iron of quartzose hematites. in 
a. Rich in iron (“soft hematite ores”). Most abundant bs 
the Marquette Region, although absent from the magneti¢, pe 
trict about Lake Michigamme. Also found in the Menomm™ 
egion. 
al. With little or no manganese—34, 35. A = — 
variety, rich in iron, and containing four per cent of W® 
occurs in the Menominee Region—1 
her in manganese (specimens of pure pyrolusite bem. 
a2. Ric 
sometimes found)—24, 25. 
, 
ie 
on 
a 
