PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 351 



Slate. Quartz. Schist.] 



No. 297. SLATE. (Chloritic.) 



Vermilion lake. Locality uncertain. Minnesota Company's mining location. Perhaps on Birch point. 

 Ref. Annual Report, ix, page 98; Annual Report, xviii, pages 20, 21; Annual Report, xix, pages 125, 127. 



Meg. Specimen missing (used for assay). 



Mic. The section shows a distinct parallel structure, evinced by the prevailing 

 direction of the chlorite shreds. It embraces much decayed feldspars, -with minute 

 mica scales, a little quartz in the form of independent, yet sub-rounded, sizable grains, 

 and a noticeable amount of siderite, which is easily diagnosed by its high refractive 

 power. It is usually clear and unoxidized, yet occasionally some dark accumulations 

 are enclosed in it. It has an evident, fine and regular cleavage in two directions. 

 This structure again distinguishes it from calcite, which generally shows only a 

 coarse and rather distant cleavage in rigid heavy lines, or is destitute of evident 

 cleavage. 



Remark: This existence of siderite in the rocks of the region, sheared " quartz- 

 porphyries," graywackes, clay slates and chlorite slates, as well as in the jaspilytes, 

 is worthy of special note, as it is the source, as supposed by some geologists, of the 

 iron ore lodes of the Vermilion range. (See chemical analysis under No. 395). 



One section. 



Age. Archean (Keewatin). N. H. w. 



No. 398. QUARTZ. (Vein.) 



"The quartz from this mining location occurs in the joints of the rock, in irregular deposits, but generally 

 coincident with the slatiness. It carries considerable pyrite, which is also scattered through the slates." Same 

 locality as No. 397. 



Ref. Annual Report, ix, page 98; Annual Report, xviii, pages 20, 21; Annual Report, xix, pages 125, 127. 



Meg. Specimen missing (used for assay). 

 Age. Vein in Archean (Keewatin) rocks. 

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



No. 399. CHLORITE SCHIST. 



"Talcose (?) slate,.from Simond.s' location. This is farthest northwest (or west), and about four miles from 

 the outlet of the lake; and between this and the Minnesota Company's location was that of Nobles, numerous 

 islands occurring all along. This number represents the country rock. It is siliceous, and contains scattered 

 nests or broken layers of white quartz, both coincident with the slates and in the diagonal jointage. Pyrite is 

 scattered through the quartz, and through the slates, and particularly in a line of contact where they unite, the 

 quartz becoming gray." Vermilion lake. The exact location is uncertain, but it may be on Silver (Shonea) 

 island (southwest corner of sec. 31, T. 63-16 W.), where mining for gold was carried on. (See map in vol. iv, page 

 523.) 



Ref. Annual Report, ix, page 98; Annual Report, xviii, pages 20, 21. 



Meg. Specimen missing (used for assay). 



Mir. The section is composed of calcite, chlorite, minute scales of sencite, and 

 very fine grains of quartz and probably also feldspar. Considerable opaque material 

 which is almost black in transmitted light and gray in reflected light, is present in 

 small patches and also in minute specks. The characteristic feature of the rock is 



