640 GEOLOGY OF CENTRAL WISCONSIN. 



which is very much altered. The grains of quai-tz appear angular, and contain numer- 

 ous fluid inclusions. 



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

 E. qr. Sec. 28, T. 29, E. 5. E., Marathon couniij. Light and dark-green; taloose or 

 cMoritic texture; wai-ped schistose structure. Hardness about 4. Under tlie microscope 

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

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

 syenitic and hornblende schist ash. 



958. Talco-Mica-Sohist. Archjsan. Catling on the W. V. R. R., three 

 miles north of Junction City, Sec. 2i, T. 25, R. 6 E. Light drab; talcose texture on 

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

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

 the microscope the light scales of talc are liardly distinguishable fi-om 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. Arch^an. Catting on W. V. R. R.,tioo and a 

 half miles north of Junction Citi/. Sec. 26, T. 25, B. 6 E., Portage county. 

 Dark-green; fine-gi-ained .texture. A fracture in the du:ection of the cleavage glistens 

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

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

 showing then- usual proneness to twin. The angular grams of quartz and leaves of 

 mica (bioUte) are readily distinguished, also opaque crystal cul)es of pyrites. The separ- 

 ate mineral ingredients are arranged in bands or layers. 



962. Mica-Schist. AROiiiEAN. From catting on W. V. R. R., one and a half 

 miles north from Jnnrtion 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 tlio 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. Arcti/eau. From a cutting on the W. V. R. R., ^i 

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

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

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

 amphibolo, quartz and mica, also a little chlorite. 



964. Hornblende-Schist. ARcniEAN. 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. Arcu^an. From east side of Wiscomin rivr-r, 5 miles 

 south of Mosinee, T. 26, R. 7 E., Marathon county. Grayish-gi-een; aphanitic text- 

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

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

 altered crj-stals of felspar, winch are usually very indistinct, only the faint outlines re- 

 maining, With a power of 600 diameters the smaU pale-greenish leaves of chlorite ai-e 

 \-isible, also numerous minute particles of magnetite. 



970. Quartz-Porphyry. Arch/ean. From thehed of Yellow river, 3 miles north 

 of Dexteralle, 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- 



