PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 359 



Quartz ore. Gold ore. Dioryte.] 



No. 421. QUARTZ ORE. 



Vermilion lake; perhaps N. W. ^ sec. 6, T. 62-16 W. This rock is missing, having been used in making 

 assay of the Vermilion Lake gold ores. (See Annual Report, xviii, page 19.) 

 Ref. Annual Report, ix, page 101. 



N. H. W. 



No. 422. MICA SCHIST. 



Same place as No. 421. 



Ref. Annual Report, ix, page 101. 



Meg. A very fine-grained, micaceous, schistose rock, of a glistening, somewhat 

 silky lustre, but which, notwithstanding its fineness, is probably of the same nature 

 as the biotite schists of the region. 



Mic. Consists of quartz, biotite, muscovite, calcite; the biotite is frequently occu- 

 pied by a web of sagenite needles which form the characteristic angles of 60 with 

 each other. 



One section. 



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



No. 423. GOLD ORE. 



9 



Nobles' mining location, Vermilion lake; apparently on the south shore of Black Duck point; N. W. % 

 sec. 9, T. 62-16 W. 



Ref. Annual Report, ix, page 101; Annual Report, xv, page 282; Annual Report, xviii, page 20; Annual 

 Report, xix, pages 125, 127. 



Meg. The samples consist of two rocks, evidently the country rock and some 

 vein material. The former is green, fine, calcareous, pyritiferous, apparently 

 sericitic. The latter is largely of calcite, with quartz and a little pyrite. 



Mic. The slide was made evidently from the green portion of the rock, and 

 while chlorite gives it color, it consists, still, largely of calcite. There is also a notable 

 amount of a fresh secondary feldspar, and of some mica, less refractive than calcite, 

 apparently muscovite. The calcite is not in large crystalline individuals, but in 

 aggregates of many small crystals that interlock. 



One section. 



Age. Archean (Keewatin). 



Remark. See chemical analysis under No. 395. N. H. w. 



No. 424. DIORYTE. 



Vermilion lake; perhaps on Birch point, a little west of the Minnesota Company's mining location; repre- 

 sents a local variation, apparently, in the slates of the region. 

 Ref. Annual Report, ix, page 102. 



Meg. A hornblendic, barely schistose, green rock of rather fine grain. 



Mic. The hornblende is the most conspicuous mineral, making the rock resemble 

 the rocks already described from the east side of Vermilion lake (No. 380). Some of 

 it is nearly colorless, and most of it is light green. It does not show any idiomorphic 



