640 GEOLOGY OF CENTRAL WISCONSIN. 



which is very much altered. The grains of quartz appear angular, and contain nuraer' 

 ous fluid inclusions. 



953. Chloritic Schist (provisional). LAUREXTIAX. Falls of Big Rib river, N. 

 E. q>: Sec. 28, T. 29, R. 5. E., Marathon county. Light and dark-green; talcose or 

 chloritic texture; warped schistose structure. Hardness about 4. Under the microscope 

 a section of the specimen appears to consist largely of altered crystal fragments of fel- 

 spar, and grains of quartz, scattered in a greenish chloritic base. The rock is probably a 

 syenitic and hornblende schist ash. 



958. Talco-Mica-Schist. ARCHAEAN. Cutting on the W. V. R. R., three 

 miles north of Junction City, Sec. 24, T. 25, R. 6 E. Light drab; talcose texture on 

 lamination planes and arenaceous across the grain; cleaves readily into irregular finely- 

 ribbed plates ; somewhat altered, and emits a strong clay odor when moistened. Under 

 the microscope the light scales of talc are hardly distinguishable from those of mica, but 

 the dark ones of the latter are more easily recognized. The section is composed largely 

 of small angular grains of silica. The argillaceous odor is due to the numerous de- 

 composed fragments of felspar. 



961. Calcareous Mica-Schist. ARCHAEAN. Cutting on W. V. R. R., two and a 

 half miles north of Junction City. Sec. 26, T. 25, R. 6 E., Portage county. 

 Dark-green; fine-grained texture. A fracture in the direction of the cleavage glistens 

 with bright, dark greenish-black scales of mica. A lump thrown into acid effervesces 

 briskly, leaving a friable mass. Under the microscope the crystals of calcite are striated 

 showing then: usual proneness to twin. The angular grains of quartz and leaves of 

 mica (biolite) are readily distinguished, also opaque crystal cubes of pyrites. The separ- 

 ate mineral ingredients are arranged in bands or layers. 



962. Mica-Schist. ARCHAEAN. From cutting on W. V. R. R., one and a half 

 miles north from Junction City, Sec. 35, T. 25, R. 6 E., Portage county. Light drab; 

 fine-grained, arenaceous texture across the lamination; slightly shimmering along the 

 schist planes. The minute scales of mica are hardly recognizable to the naked eye. 

 Under the microscope, in the polarized light, a section of the specimen appears brightly 

 colored with angular grains of silica. The base of the rock presents a dirty appearance, 

 and scattered in it are the brownish leaves of mica and a few altered crystal fragments 

 of felspar. 



963. Hornblende-Schist. ARCH/EAST. From a cutting on the W. V. R. R., % 

 mile north of Junction City, Sec. 35, T. 25, R. 6 E., Portage county. Dark-green. It 

 is somewhat altered and has a dirty lock. The single mineral ingredients can barely 

 be recognized with the naked eye, but under the microscope are plainly visible the 

 amphibole, quartz and mica, also a little chlorite. 



964. Hornblende-Schist. ARCHAEAN. From a cutting on the W. V. R. R., 7 1-2 

 miles south from Junction City, north part, of T. 23, R. 6 E., Wood county. Dark 

 grayish-green; fine-grained, crystalline-texture; schistose structure and jointed; 

 weathers to a drab. Under the microscope it appears to consist mostly of amphi- 

 bole. Several small grains of quartz are contained, also a little chlorite. 



968. Chloritic Rock. ARCH.EAN. From east side of Wisconsin river, 5 miles 

 south of Mosime. T. 26, R.7E., Marathon county. Grayish-green; aphanitic text- 

 ture; very jointed and apparently schistose. Under the microscope the base of the sec- 

 tion presents a moss-like microcrystalline structure, and scattered through it are highly 

 altered crystals of felspar, wlu'ch are usually very indistinct, only the faint outUr.es re- 

 maining. With a power of 500 diameters the small pale-greenish leaves of chlorite are 

 visible, also numerous minute particles of magnetite. 



970. Quartz-Porphyry. ARCHAEAN. From the bed of Yellow river, 3 miles north 

 of Dexterville, Sec. 3, T. 22, R. 3 E., Wood county. Light pea-green; massive; resem- 

 bles some of the quartzites. Several crystal-facets of felspar may be seen, also an occa- 



