350 THE GEOLOGY OP MINNESOTA. 



[Schist. Clay slate. Quartz- 



No. 394. SERICITE SCHIST. 



Same locality as No. 389. 



Ref. Annual Report, ix, page 97. (See remarks under No. 389.) 



Meg. A siliceous, very fine-grained sericite schist, greenish gray in color. 



Mic. The section is very fine grained. It consists of scales of Sericite, and a little 

 chlorite, and grains apparently of both quartz and feldspar. These grains make up a 

 large portion of the section, but their exact nature cannot be determined. The section 

 contains specks, gray and semi-opaque in reflected light, which under a high power 

 are seen to be made of aggregates of very fine, rather highly refractive grains. The 

 nature of these cannot be made out. They have elsewhere been referred to epitlote, 

 but may be siderite. 



One section. 



Age. Archean (Keewatin). u. s. G. 



No. 395. CLAY SLATE. 



Vermilion lake; New York Mining Company's location; S. W. J S. W. J sec. 26, T. 62-16 W. 

 Ref. Annual Report, ix, page 98; Annual Report, xviii,page20; Annual Report, xix, pages 125, 127. This 

 locality is also described in the Fifteenth Annual Report, pages 280, 281. 



Meg. A gray, very fine-grained clay slate. 



Mic. The section is composed very largely of minute grains of quartz (with 

 probably feldspar also); chlorite and a little sericite are also present. There are .two 

 particularly interesting features in this section. The first is the presence of much 

 siderite in rough rhombs and irregular areas. Frequently a yellowish stain (limonite) 

 accompanies the siderite. The second feature is the presence of numerous minute 

 rutile crystals. These give bright polarization colors, and many heart-shaped twins 

 are seen. One section. 



Chemical analysis. Nos. 395, 396, 397, 398, 400, 423 and 428 represent some of 

 the gold ores of the Vermilion lake gold excitement of 1866. These specimens were 

 assayed together, as one sample, by Prof. C. F. Sidener and no gold nor silver was 

 found. 



Age. Archean (Keewatin). u. s. o. 



No. 396. QUARTZ. (Vein.) 



" 'Gold ' quartz, from the above mining location. This is white. It is scattered in the joints and irregular 

 veinings in No. 395, similar to what may be seen in many places about Vermilion lake. (See report for 1878, 

 page 23.)" 



Ref. Annual Report, ix, page 98; Annual Report, xviii, page 20; Annual Report, xix, pages 125, 127. 



Meg. Specimen missing. 



No section. 



Age. Vein in Archean (Keewatin) rocks. 



Remark. See chemical analysis under No. 395. u. s. o. 



