614 THE GEOLOGY OF MINNESOTA. 



[Granite. Gabbro. Syenyte. 



No. 961. GRANITE. (Contact.) 



" Rock No. 961 shows the contact between the coarse syenyte like No. 953, as it occurs near the southwest 

 corner of sec. 24, T. 61-12, and the granite Nos. 955 and 959." 

 Ref. Annual Report, xv, pages 334, 391. 



Meg. A coarse-grained, sub-porphyritic, hornblende biotite granite, in sharp 

 contact with a fine-grained biotite granite. 



Mic. The slide was evidently made from the coarse-grained part of the hand 

 sample. The rock is a granite, the essential minerals being feldspar, quartz and 

 biotite. Chlorite, magnetite and sphene also occur. One section. 



Age. Archean. u. s. G. 



No. 962. GABBRO (?) 



About one fourth mile west of No. 961. 

 Ref. Annual Report, xv, pages 336, 391. 



Meg. The hand specimens vary some in grain and in general appearance. 

 Some look like fine-grained, magnetic rocks, recrystallized by the gabbro, and others 

 seem to be fine-grained gabbros. 



Mic. The rock has a granitic texture and consists of pyroxene (at least some of 

 which appears to be ortho rhombic), brownish hornblende, magnetite, feldspar and 

 quartz. One of the sections shows light colored areas in a dark background. These 

 areas are composed mainly of feldspar and pyroxene, the latter sometimes in poiki- 

 litic plates, while the background consists largely of hornblende. 



Two sections. 



Age. Cabotian(?) u. s . G. 



Remark. This rock is apparently allied to No. 960. One specimen, of which 

 no section was made, is a fine-grained heavy iron ore. N. H. w. 



No. 963. SYENYTE. (Biotitic.) 



S. W. M S. W. )4 sec. 24, T. 61-12 W., just east of the line between sections 23 an'd 24; near the north shore 

 of Birch lake. 



Ref. Annual Report, xv, pages 336, 391; Annual Report, xvii, pages 195, 207. 



Meg. Fine-grained, reddish syenyte, with some porphyritic reddish feldspars. 

 Mic. The rock is a granitic one, composed largely of feldspar, which seems to 

 be mostly orthoclase. Biotite is common, and magnetite and chlorite occur. 

 Two sections. 

 Age. Archean. v s G> 



No. 964. GRANITE. (NornMendic. ) 



"Rock No. 964 shows a coarse ayenyte, lying on No. 965, apparently conformably; No. 964A is from a vein 

 (or dike) of fine granular granite, six inches wide, running across the bedding of No. 964 and blending with No. 

 965. No. 964B is mica schist, a condition of No. 964A, in small patches." S. E. y sec. 22, T. 61-12 W.: point on 

 north shore of Birch lake. 



Ref. Annual Report, xv, pages 334, 335, 391. 



