APPENDIX MICROSCOPIC LITHOLOGY. 641 



sional small quartz crystal. Under the microscope a section of the specimen appears 

 composed chiefly of felspar, with a few crystals of quartz scattered through it. The 

 quartz resembles that contained in igneous rocks, since some of the crystals enclose, ap- 

 parently, portions of "the matrix. Their richness, however, in fluid cavities, would no 

 doubt preclude such a supposition. The felspar is somewhat altered and presents fre- 

 quently a fringy texture. A few spherulites of felspar so common to quartz-porphyries 

 may be recognized. 



992. Felspathic-Schist (provisional). ARCH^AN. Cutting on W. V. R. R., 3.7 

 miles south of Knowlton, Sec. 12, T. 25, R. 6 E., Portage county. Grayish-drab; fine- 

 grained, indefinite texture. A few minute crystal-facets are visible; emits a strong clay 

 odor when breathed upon. Under the microscope the rock appears very felspathic. and 

 some of the crystals are beautifully banded. Numerous small angular grains of quartz 

 are contained, also brownish leaves of mica, and a fibrous mineral resembling talc. 



997. Actinnlite-Schist. AKCH^AN. Cutting on W. V. R. R., 3.7 miles south of 

 Knowlton, Sec. 12, T. 25, R. 6 E., Portage county. Light-green, medium-grained,, 

 crystalline texture. The cleavage facets of the actinolite are easily recognized. It is 

 somewhat decomposed. Under the microscope the actinolite presents a reticulated 

 structure; a little quartz, felspar and chlorite are contained. 



1003. Diorite. ARCH^AN. From bed of Black river, Mormon Ripple, Sec. 3, T. 

 22, R. 3 W., Jackson county. Light-and-dark-green; weathers to a light-drab; me- 

 dium-grained texture, with coarse crystals of amphibole strewn through the mass. 

 Under the microscope the principal mineral ingredients appear to be amphibole and 

 felspar; the latter is of two kinds, plain and striated. An occasional crystal fragment 

 resembling augite is contained, also a little chlorite. 



1004. Quartzite. ARCHAEAN. From bed of Black river, Mormon Ripple, Sec. 3, 

 T. 22, R. 3 W., Jackson county. Light reddish-gray, with streaks of dark-green; 

 quartzose, vitreous texture. Under the microscope appears, in addition to the quartz, a 

 considerable number of slightly altered crystals of orthoclase and greenish leaves of 

 mica or possibly chlorite, though they are apparently the former, since they are strongly 

 diehroitic. 



1005. Felspathic Quartzite, or Granite. ARCHJEAN. From bed of Black river, 

 at Mormon Ripple, Sec. 3, T. 22, R. 3 W., Jackson county. Flesh color; medium- 

 grained texture. On a fresh fracture may be seen numerous bright cleavage facets of 

 felspar. Under the microscope the felspar and quartz appear to be about efjually di- 

 vided. The former are mostly plain crystals, and the latter enclose numerous fluid 

 cavities. 



1007. Micaceous Schist. ARCHAEAN. From the bed of Black river, at Mormon 

 Ripple, Sec. 3, T. 22, R. 3 W., Jackson county. Drab; fine-grained, arenaceous texture; 

 somewhat decomposed and emits a strong clay odor when moistened. Under the mi- 

 croscope a section of the specimen appears to consist largely of altered brownish frag- 

 ments, resembling mica. Scattered in the base are numerous small angular grains of 

 silica. 



1008. Granite. ARCH/BAN. From bed of Black river, at Black River Falls, 

 Sec. 15, T. 21, R. 4 W., Jackson county. Flesh-color, spotted with dark-green; medium- 

 grained texture. The crystal-facets of felspar and grains of quartz are plainly visible 

 to the naked eye. Under the microscope, the felspar appears to be more largely con- 

 tained than the quartz. But little mica is present. 



1412. Quartz-Porphyry. HURONIAN? Pine Bluff, N. W. qr. of the N. E. qr. 

 of Sec. 2, T. 11, R. 11 E., Green Lake county. Grayish-white; fine-grained texture, 

 and porphyritic with glassy crystals of felspar, which resemble sanadin. Under the 

 microscope, the specimen seems to be an intimate mixture of felspar and quartz. Some 

 of the felspar crystals have an appearance as if, after they were formed, they had been 

 Wis. Sun. 41 



