796 THE GEOLOGY OP MINNESOTA. 



[Quartzyte 



in diameter, which are green, rather soft and weather out more rapidly than the rest 

 of the rock. No section. 



Age. Animikie. u. s. G. 



No. 1842. QUARTZYTE. (Metamorphosed.) 



Pigeon point, one-half mile west of Little Portage bay (i. e., where Pigeon point is narrowest). 

 Ref. Annual Report, xxii, page 9. 



Meg. At this point the axis of the peninsula is composed of a dark -greenish, 

 but spotted, modified quartzyte, the spots being coincident with or caused by poiki- 

 litic crystals of some rock-making mineral, apparently some feldspar. 



Mic. While interlocking quartz makes up the greater portion of the slide, a 

 considerable area is also occupied by delessite, by feldspar (ortkoclase), by actinolite, 

 and by a yellowish-brown mineral which has the form represented by the figures 

 attached. This mineral has an irregular cleavage or lamello-fibrous structure in 

 the plane of which lies the axis K . It affects hexagonal outlines when entire, but 

 is frequently elongated in the direction of g . Its absorption is faint but distinct, 

 and is greatest when the lower nicol coincides with n g . In the identifiable optic 

 characters, except coloration, it well agrees with the usual characters of biotite. 



FIG. 47. YELLOWISH-BROWN BIOTITE IN NO. 1842. 



Quartz is sometimes in micro-pegmatitic relation with the feldspar, and the 

 latter in large reddened crystals sometimes embraces all the other minerals 

 poikilitically. One section. 



Age. Animikie. N. H. w. 



No. 1845. QUARTZYTE. (Metamorphosed.) 



From the red knob rising near the south shore of Pigeon point a little west of Little Portage bay. 

 Ref. Annual Report, xxii, page 9. 



Meg. Quartz keratophyre (Bayley). The knob exhibits -various conditions of 

 this quartzyte. 



Mic. The section shows granular quartz and spherulites of <-1hocl(t.w, with 

 hornblende and delessite. One (thick) section. 



Aye. Cabotian. 



Remark. This is a phase of the " red rock," and acts like a Cabotian intrusive, 

 and at other places forms lava flows under favorable conditions. N. H. w. 



