648 THE GEOLOGY OP MINNESOTA. . 



[PebHes. Esterellyte. Conglomerate. 



No. 1061A. INCLUSIONS OR PEBBLES PROM No. 1061. 



Same locality as No. 10C1. 



Ref. Annual Report, xv, pages 367, 390 ; see, also, Annual Report, xxi, page 51. 



Me//. A few dark, sub-angular pieces of completely crystallized rock, made up 

 almost entirely of hornblende or of hornblende and augite. No section. 



Age. Archean. u - s - G - 



No. 10G1B. ESTERELLYTE. 



Same locality as No. 10C1. 



Ref. Annual Report, xv, pages 367, 396. 



Mi'i/. Similar to No. 1061, but showing a white weathered surface in which are 

 a few large grains of quartz. No section. 



Aye. Archean. u. s. e. 



No. 1062. CONGLOMERATE. 



Near the narrows in lake No. 6, or Zeta lake, sec. 28, T. 65 6, east of Kekequabic lake. 

 Ref. Annual Report, xv, pages 368, 369, 396. 



Meg. Coarse conglomerate, with many evident large crystals of feldspar, with 

 occasional visible quartz. Forms hills fifty to seventy-five feet high. 



Mir. This consists of the same elements in evidently fragmental state as seen 

 in the foregoing described porphyry (No. 1061) from Kekequabic lake. The augite 

 is changed to hornblende and the feldspars are clouded by decay, containing ka<>/i. 

 They are much twinned, often in remarkable combinations, as in rock No. 1061. 

 These elements, though large and conspicuous in numerous large grains, are also of 

 all smaller sizes, descending to the size of the grains of the matrix. They rarely, or 

 never, are ingrown or interlock, except where twinned originally, but are separated 

 uniformly by spaces filled with the fine elements. They are palpably all fragmental 

 grains, and did not have their birth in the places in which they now lie except where 

 they are embraced in some of the pebbles. The fine matrix is composed largely of 

 secondary feldspars, but it is evidently more nearly in its original fragmental state 

 than about Kekequabic lake, a fact that can be attributed to the non-action of great 

 metamorphism at this point. This difference is also observable in the non-zoned con- 

 dition of the large feldspars, and the absence of fibrous secondary enlargements on 

 the hornblendes, which simply show, occasionally, the old augite outlines. 



As to the species of the feldspar, extinction in two instances on the axis ,, 

 indicate and^inc or andesine-oligoclase, and one test on ><, gave 20", which is near 

 nlbite. Allowing for error and for some obliquity in the section, it can only be said 

 that these observations show a feldspar of medium basicity. The remarkable 

 twinning, in which the albite bands vary in width rather suddenly along their greater 

 extension, and are confusedly intersected- by pericline bands, and are interrupted by 



