THE EASTEliN AREA. 403 



lu tliiu section, a tine gniiiicd groiuulniass ofciiiartz, chlorite, kaoliu, pyrite, coa- 

 taius uumerous fragments of (quartz and feldspar, the latter being more plentiful. 



Section near range line between B. 42 W., and B. 43 W., Michigan. 



33. Recomposed grauitd, from a low horizon. Si)ccimen 12592 (slide 5347), 1700 

 N., 232 VV., See. 24, T. 47 N., K. 43 W., Michigan. 



The rock is pink, white and bhick mottled, c(jarse grained, massive. In nearly 

 all re.si)ects this rock is iu appearance like a granite. It weathers to some depth to a 

 dark brown color. 



The section, if not examined closely, would be taken for a coarsely crystalline 

 granite. The minerals abundantly present are quartz and feldspar, the latter being 

 orthoelase, microcliue, and plagioclase. In subordinate quantity are chlorite, pyritt^, 

 and ferro-dolomite. In the major portions of these sections the minerals are in large 

 complex granite fragments, which are often crowded so close together as to make it 

 difficult to follow their outlines. The interstitial material is chietly tinely crystalline 

 quartz, but mingled with this is a little ferro-dolomite. In some places this intersti- 

 tial material is in quite large areas and contains distinct fragments of quartz and feld- 

 spar. Many of the striated feldspars show finely the eliects of bending and fracture; 

 some grains are bent but not broken, while others are fractured, each of the frag- 

 ments in such cases showing bending due to the strain before fracture occurred. 



34. Ferro-dolomitic chert, interstratilied with 3.3. Specimen 12593 (slide 5348), 

 1700 N., 232 W., Sec. 23, T. 47 N., 11. 43 W., Michigan. 



The iock is greenish gray, medium grained, and massive. 



A large part of the section, constituting a baitkground, is (u)mitosed of flnely 

 crystalline cherty silica and somewhat coarsely crystalline fierro-doloinite. Where the 

 silica is in excess, the carbonate occui's largely in well outlined rhombohedra. Con- 

 tained in the background are angular fragments of a much altered, fine grained por- 

 phyrite. 



35. Ohert-breccia, from a low horizon, north of 34. Specimen 12594 (slide 5349), 

 1748 N., 232 W., Sec. 24, T. 47 N., II. 43 W., Michigan. 



The rock is a gray and green chert-breccia, which contains between the chert 

 fragments particles of coarsely crystalline quartz. 



Rounded and angular fragments of chert of greatly varying sizes compose a large 

 part of the section. Mingled with these chert fragments are many siini)le grains of 

 quartz, which are widely enlarged and the enlargements of which merge into the 

 matrix. Both classes of fragments are cemented with finely crystalline cherty silica, 

 which is almost exactly like tliat in the chert fragments, and were it not for the iron 

 stained outlines of the latter it would be impossible to separate them from the matrix 

 in which ihey are contained. 



