GEOLOGICAL EXPLORATIONS AND LITERATURE— 1841. U 



the fraiiite iusensiljly <i;'riules, iKiriibleiule-slates, talcose and micaceous 

 slates and clav-slates, and Hnally (jnartzites. 'I'lie series dips iiTeiiularly to 

 tlie south and southeast, while the cleavag-e of the slates is very unit'orni 

 to the north (p. 168). These "metamorphic" rocks are confined ex(du- 

 sively to the range of hills lying- upon the southeast side of the g-ranitic 

 rocks. They occupy a belt of country having- an average Avidth not 

 exceeding fi to 8 miles. The precise limit of the series to the southwest 

 is unknown. The southeastern boundary is tlie Chocolate River. The 

 alternations of the different members of the series are so complicated tluit 

 the author does not attempt to describe them. He contents himself witli a 

 description of the ([uartzite, which he finds to be granular and compact, 

 and a statement with regard to the serpentinous rock lying immediateh' . 

 south of the granite. Tins rock has a regular-jointed structure resemljling 

 stratification. In composition it is very close to greenstone, since it consists 

 essentially "of granular feldspar and hornblende, Avith which serpentine 

 is intimateh- blended. This rock only occurs in the talcose slate as we 

 approach the granitic region, and possibly a more close examination may 

 show it to be a simple series of dikes lying parallel to tlie line of cleavage 

 of the slate rocks" (pp. 182-183). Like the primar}- rocks, the metamorphic 

 ones are traversed by trap dikes. 



The serpentinous rocks to which the reference is made are the green- 

 stone-schists which were so long regarded as ])art of the sedimentary series, 

 and whose origin was a matter of doul)t laitil CI. H. Williams proved them 

 to be altered basic tuffs. The mica-slates and clay-slates and the quartzites 

 are members of the Marquette series. 



In the economic portion of the report the State geologist refers to tlie 

 value of the granite and the greenstones as building materials, and gives a 

 list of the nnnerals found in the primary and metamorphic series. Among 

 those in the metamorphic series novaculite and hematite are mentioned, but 

 the latter is not thought to be of much value. "Although the hematite is 

 abundantly dissenfinated through all the rocks of the metamorphic group, 

 it does not appear in sufiicient quantity at any one point that has been 

 exannned to he of practical importance" (])p. lOU-lUT). 



