740 THE GEOLOGY OP MINNESOTA. 



[Taoonyte. Conglomerate. Hematite. 



separated permanently into angular pieces which again were encircled by the same 

 kind of bands. This shrinkage is also shown in figure 10. Some of the pebbles are 

 but scantily furnished with the encircling bands. In those cases the nuclei are not 

 distinctly amorphous, but are finely granular and ultra-microscopically crystalline 

 like " flint " or devitrified glass. Yet some of these also appear to have had, and to 

 have lost, such encircling bands. In such flinty pebbles the hematite of the rock is 

 distributed as a crystalline powder, greatly in contrast with the hematitic blotches 

 and opaque nuclei of the other pebbles. In some cases, however, these contrasts 

 appear in the same pebble, showing that whatever was the nature and origin of one 

 was also the nature and origin of the other. 



It is impossible to say that there are any other minerals than quartz and hematite 

 in these slides. The former, in an interlocking mosaic, fills all the spaces between 

 these oolitic 1 pebbles, penetrates within the bands, and into the nuclei. In the bands 

 it embraces the hematitic powder and extinguishes in the "patchy" manner of apob- 

 sidian. In the nuclei it variously mingles with the hematite, but sometimes it forms 

 microscopic spheruliths whose rays, having a mass of hematite at the centre, are of 

 negative elongation, and hence appear to be of chalcedony. This negative character 

 cannot be affirmed of the interlocking quartz in general, although it has frequently 

 been designated chalcedonic quartz; with one nicol it shows a faint absorption or 

 pleochroism. 



It seems impossible to explain these taconitic pebbles except by assuming that 

 they were originally volcanic ash or sand. Compare Part III for further consider- 

 ations. Compare No. 1630A. N. H. w. 



No. 1532. CONGLOMERATE. 



Same locality as No. 1527. Underlies the ore. 

 Ref. Annual Report, xviii, pages 15, 60. 



Meg. The matrix of the conglomerate is a coarse, gray, granular quart/ v I r. 

 The pebbles are small, rarely over half an inch in diameter. They are of quartz 

 (largely), dark, fine-grained schist or argillyte, greenstone and red hematitic rock. 

 No section. 



Age. Animikie (Pokegama quartzyte member). r. s. o. 



No. 1537. HEMATITE. 



N. W. Y* N. W. 14' sec. 21, T. 56-24 W. 

 Ref. Annual Report, xviii, pages 18, CO.* 



Meg. A red, slaty, impure hematite, more or less granular like taconyte. Gives 

 forty-seven per cent of metallic iron. No section. 



.\;/p. Animikie (iron-bearing member). u. s. <;. 



On page fiO the locality is, by a typographical mistake, given as T. 511-14 instead of T. 



