260 THE GEOLOGY OF MINNESOTA. 



[Diabase. Aporhyolyte. Porphyry te. 



Magnetite is present, but is not nearly as abundant as the hematite. The brown color 

 of the rock in hand specimens is due to the abundance of hematite. 



One section. 



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



No. 211. DIABASE. (Lustre-mottled.) 



Cow's Tongue point, the point next west of Kimball's creek, S. E. % sec. 9, T. 61-2 E. 

 Ref. Annual Report, ix, pages 54, 55; Annual Report, x, page 43. 



Meg. Similar to No. 210. The hand sample shows a water-worn surface which 

 is blotched with lighter areas. 



Mic. Essentially identical with No. 210, but the augite is in larger plates, and 

 the magnetite is more abundant, but hematite is present in large quantities. 



One section. 



Age. Cabotian. u. s. G. 



No. 212. APORHYOLYTE. 



In the bay next east of Cow's Tongue point, after a short pebbly beach, this rock forms a low outcrop. 

 Ref, Annual Report, ix, page 54; Annual Report, x, page 43. 



Meg. A red or brownish red rock with scattered porphyritic crystals of some 

 glassy feldspar, but no quartzes. 



Mic. This rock much resembles the Palisade rock (No. 139), but in the absence 

 of original quartzes it is probably less acid. It is also the same rock as No. 203. 



One section. 



Age. Cabotian. N. H. w. 



NO. 213. PORPHYRYTE. 



From the extremity of Fish Hook point, near the centre of sec. 6, T. 61-3 E.; eleven miles from Grand 

 Marais. Lies as an overflow, and is visible under the water toward the west for some distance, cut by dikes. 

 Ref. Annual Report, ix, page 54; Annual Report, x, page 43. 



Meg. Dark brown, easily splitting rock, which has scattered, light-colored 

 feldspars in a fine matrix. This rock is fissile, horizontally, or obliquely to the main 

 structure, which dips toward the lake. Nos. 213, 214 and 215 may be included 

 in one general description, since they occur on the same general expanse of beach 

 extending from the point westward for nearly half a mile. It is firm against the 

 hammer and against the weather, but is filled with old cracks and joints that make 

 it almost impossible to get a fresh break. It has a red color outwardly, near the 

 water, except in the joints which are iron-shot (so called by Norwood) and blue 

 black. It is finely porphyritic with stellar spangles of feldspar and with isolated 

 crystals that weather nearly white. 



Mic. A few olivines, numerous feldspar microliths and minute augites( ?) were 

 generated in this rock before the consolidation. There remained, however, a large 

 amount of undifferentiated magma, which now renders the slide dark and obscure 



