600 THE GEOLOGY OP MINNESOTA. 



[CAiptonyte. Breccia. Jaspilyte. 



a few areas of fibrous hornblende encroached upon by epidote; these seem to represent 

 some original, porphyritic, ferromagnesian constituent. A few larger quartz grains 

 occur, and there is one which shows an approach to a bipyramidal form. 



One section. 



Age. Keewatin. tr. s. G. 



No. 915. CAMPTONYTE(?) 



"Greenstone, from dike cutting the graywacke near the railroad, southeast of Tower; sec. 33, T. 62-15." 

 Ref. Annual Report, xv, pages 271, 273, 389. 



Meg. A fine-grained, compact, massive, grayish-green rock. It weathers to a 

 greenish gray. 



Mic. The section shows a rather fine-grained rock, whose chief component is 

 feldspar. This occurs in irregular grains and forms the background of the rock. 

 The feldspar is sometimes untwinned and sometimes shows albite twinning. Its 

 species was not carefully determined, but equal extinction angles in twinned sections 

 indicate a feldspar near andesine or perhaps andesine-oligoclase. Hornblende is 

 abundant. It is brownish green and pale green to almost colorless. The brownish- 

 green hornblende occurs in elongated prisms, whose size in cross sections is consid- 

 erably less than that of the feldspars. The prismatic planes on this brownish-green 

 hornblende are often developed, but the terminal planes rarely. Frequently these 

 hornblendes have borders and fibrous elongations of the pale-green hornblende, and 

 the latter occurs in irregular masses and small fibres abundantly throughout the 

 section. Epidote is common, and there is a little iron ore. One section. 



Age. Keewatin. u. s. G. 



No. 916. BRECCIA. (HematHic.) 



Breitung mine, Soudan. 



Ref. Annual Report, xv, pages 250, 389; Annual Report, xvii, pages 194, 215. 



Meg. A rough, heavy rock, brecciated, and composed of small fragments of 

 hematite in a cement of the same. Scattered all through the rock ara small, irreg- 

 ularly shaped areas of a soft, white, earthy substance. Some of this substance was 

 examined under the microscope and found to consist of a very finely divided, gray, 

 practically isotropic material. Specimens collected later under this number show 

 a breccia of jaspilyte. No section. 



Age. Keewatin. u. s. G. 



No. 917. JASPILYTE. 



From the extreme eastern extension of the ridge affording No. 868; sec. 32, T. 62-15 W., Tower. 

 Ref. Annual Report, xv, pages 268, 389. 



Meg. Brecciated, somewhat crumbling, white, black, gray and red jaspilyte. 



No section. 



Age. Keewatin. u_ s G 



