550 THE GEOLOGY OP MINNESOTA. 



[Granite. 



donic " quartz, the former mineral forming the most of the vein, and, where the 

 quartz occurs, making the sides of the vein, the quartz being in the centre. There 

 are also a few areas, probably pseudamygdules, of quartz. 



Mic. The sections show a much altered diabase porphyryte. The minerals are 

 mainly feldspar, hornblende, epidote, chlorite and iron ore. The chlorite is frequently 

 developed in the feldspars, which are also kaolinized. 



Three sections. 



Age. Cabotian. u. s. G. 



No. 799. GRANITE (with Jiorriblende ). 



"Saganaga lake. The first island on entering the lake from the east." S. % N. E. J^ sec. 4, T. 66-4 W. 

 Ref. Annual Report, ix, page 84; Annual Report, x, page 106. 



Meg. Coarse-grained, gray granite, composed of feldspar (white to pinkish), 

 quartz (in large grain) and hornblende. A typical sample of the Saganaga granite. 

 Mic. Same rock as No. 316. 

 Three sections. 

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



No. 800. GRANITE (with Iiornblende). 



Falls of Gunflint river at the first portage going north from Gunflint lake. N. E. J^ sec. 13, T. 65-4 W. 

 Ref. Annual Report, ix, page 83; Annual Report, x, page 106. 



Meg. Rock like No. 799, except that No. 800 has the hornblende more altered 

 and more epidote developed. 

 Mic. Same as No. 315. 

 One poor section. 

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



No. 801. GRANITE (ivithbiotite and hornblende). 



Prom S. E. % sec. 17, T. 35-30, about two and a half miles southeast of St. Cloud, on the east side of the 

 Mississippi river. 



Ref. Annual Report, x, pages 106, 107; Bulletin ii, pages 85-87. 



Meg. A coarse-grained, gray granite composed essentially of feldspar (white to 

 pinkish), quartz, hornblende and biotite. 



Mic. M. E. Wadsworth's description of this rock is as follows:* 

 "A dark-gray, coarsely -crystalline rock, composed of hornblende, biotite, pinkish 

 and gray feldspar, quartz and magnetite. Under the microscope it is seen to be com- 

 posed of the above minerals with titanite, apatite and microliths. The feldspar is in 

 part plagioclase and in part orthoclase, but in both cases the feldspar material seems 

 to be of a secondary origin, replacing other feldspars and in part retaining their 

 cloudy kaolinized material and striations. The feldspar also, in places, shows some 



Bulletin U, pp. 85-87. 



