300 THE GEOLOGY OF MINNESOTA. 



[Diabase. Barite. 



that it was and that the rock was a fine-grained diabase. The section shows one 

 grain of pyrite. 



One section. 



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



No. 287. DIABASE. 



From the big dike (like No. 274), the axis of Pigeon Point peninsula, near the location of Kindred and 

 Baker's barite vein. (Compare No. 1843.) 



Ref. Annual Report, vii, pages 16, 17; Annual Report, ix, page 69; Bulletin ii, page 96. 



Of this rockWadsworth says: " Has a section composed of plagiodase, diallage, 

 magnetite, altered olivine, and other secondary products. The olivine is replaced by 

 reddish and yellowish brown serpentine, showing the usual network or ' maschen- 

 structur ' of serpentine, replacing olivine along a network of fissures. The diallage 

 has suffered considerable alteration, is of a cloudy, brownish color, and is in part 

 replaced by biotite, chlorite, etc." 



The feldspar, which, having on 010 an extinction angle of 20, seems to be 

 labradorite, appears to have embraced, in some instances, small amounts of the 

 uncrystallized magma, which is now converted to a greenish and grayish substance 

 which gives the interference figure of a possible monoclinic mineral, but charged, 

 for the most part, with magnetite. In some cases the result of change in the olivines 

 is a highly absorptive, brownish yellow, cleaved mineral, which may be the same 

 that has been referred to already as bowlingite. Augite distinctly ophitic. 



Two sections examined. 



Age. Cabotian. 



Remark. In another section of this rock, there is much less decay; the augite is 

 ophitically related to the feldspar, and no olivine is apparent. N. H. w. 



No. 288. DIABASE. 



"Fine, green rock from the shaft at the barite vein," Pigeon point; probably in S. E. % sec - 28, T. 64-7 E. 

 Baker and Kindred's location. 



Ref. Annual Report, vii, pages 16, 17; Annual Report, ix, page 69. 



Meg. A very fine-grained, dark-gray, diabasic rock. 



Mic. The section shows small lath-shaped plagioclases, considerably altered, in 

 a groundmass of greenish and yellowish alteration products, which are hornblende, 

 chlorite and magnetite. No augite is now present, although it probably was originally. 

 Some unindividualized interstitial material may have also occurred. 



One section. 



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



No. 288A. BARITE, ETC. (Vein material.) 



From the shaft. Same locality as No. 288. 



Ref. Annual Report, vii, pages 16, 17; Annual Report, ix, page 69. 



