1016 THE GEOLOGY OP MINNESOTA. 



PLATE V. 



Page. 

 FIGURE 1 Gabbro, showing olivine (one crystal in detached sections) embracing 



feldspar in a poikilitic manner. Rock No. 1829, about 2 1 5 793 



PIG. 2 Graphic granite, coarse. Rock No. 1891, about Y 805 



FIG. 3 Taconyte, showing apobsidian sand in a groundmass of fine interlocking 



quartz. Rock No. 2138, about 2 T 5 - 845 



FIG. 4 Quartz-porphyry, showing secondary feldspar grown on old feldspar. 



Rock No. 2275, about i \ s -. The old feldspar is crowded with sericite 883 



FIG. 5 Quartz-porphyry (granitic), showing isolated feldspar fragments in a 



regenerated matrix. Rock No. 2276, about 2 T 6 884 



FIG. 6 Gabbro, both granulitic and ophitic, with grauophyric quartz. Rock 



No. 2064, about \ 5 835 



FIG. 7 Granite, showing microcline permeating and surrounding the old feldspars. 



Rock No. 1515, about - 2 T 5 ' 35 



FIG. 8 Esterellyte, showing the porphyritic manner of the feldspars of No. 1061. 



Photograph of No. 776G. Three-fourths natural size. Compare No. 766G 904 



FIG. 9 Tuff. Gunflint river. Rock No. 307, about 8 T 6 309 and 994 



FIG. 11 Taconyte in flint. Rock No. 433H, about \ 1005 



