154 THE GEOLOGY OP MINNESOTA. 



[Vein matter. Porphyryte. Calfitc. 



Meg. Almost identical with No. 63. 

 No section. 



Age. Cabotian. u. S..G. 



No. 64A. VEIN MATTER (from No. 64). 



Kef. Annual Report, ix, page 20. 



The specimen shows a vein about half an inch thick, largely consisting of calcite, 

 but also containing purple and green flnoriti'. When collected this was also said to 

 contain burn id', and it can be distinguished still on the hand sample. 



.!'/''. Vein in Cabotian basalt. N. H. w. 



No. 65. PORPHYRYTE (?) < l>i<ii>*e. ) 



Duluth. Evenly bedded, many jointed, forming bluffs of eighteen to twenty feet, holding large calcite 

 nodules. 



Ref. Annual Report, ix, pages 20, 21. 



A brick-red, very fine-grained rock holding small, red, porphyritic plagio- 

 clases, which are in part replaced by epidote and chlorite. These two minerals also 

 occur in the rock in small irregular areas. 



Mic. The porphyries feldspars are very highly altered, but in places show the 

 remains of polysynthetic twinning lamellae. The groundmass of the rock has the 

 usual red color and consists of chlm-itr, utai/m-fifc, }/<'itit/fr, mlcitc and i/itmiz; the 

 last mineral is abundant and forms the ultimate background of the section, frequently 

 including the other substances poikilitically. In the groundmass are also microliths 

 of feldspar. Many of these have no effect on polarized light and can be recognized 

 only by their form, being now a mass of red material often penetrated by the adja- 

 cent quartz areas. 



One section. 



A</?. Cabotian. u. s. G. 



No. 65A. CALCITE. ( ('ri/ 



[A large collection was made of crystals from nodules lying nearly loose in cavities in No. 65. They were 

 shipped at Duluth, but were never received at Minneapolis. ] 



Ref. Annual Report, ix. page 20. N. H. W. 



No. 66. PORPHYRYTE. (Amygdaloidal. ) 



A modification of, though probably overlying, No. 65. 

 Ref. Annual Report, ix, page 21. 



Mic. The reddened fd(l*]>rx, their very finely ferrated matrix, the fineness of 

 the texture, the prevalence of quartz, as a background for the fine minerals of the 

 matrix, and the quartz fillings of the amygdaloidal cavities, denote that this porphy- 

 ryte was originally glassy, and would properly be styled zirkelyte. 



A i/r. Cabotian. N. H. w. 



