414 THE PENOKEE lEON-BEAEING SERIES. 



abundance of secondary kaolin and sniaragdite these rocks are exactly like 

 the diabases to the westward; but in the large development of chlorite and 

 epidote there is a dift'erence. In nearly every section minerals are found 

 included in the feldspars. Frequently within the chlorite has dcvt'lopcd the 

 epidote, but at times the alteration seems to have been directl}' tVoiu feldspar 

 to epidote, in which case the epidote is in small granules. Biotite and 

 quartz are infrequently present as secondary products in the feldspar. 



The minerals secondary to the augite are the same as those included 

 by the feldspar, with the exception that quartz is absent; but as the augite 

 is much fresher than the feldspar, the quantity of secondary material from 

 this source is nuich less. Chlorite and amphibole are at times both abun- 

 dant. Next in importance to these is biotite, which in one or two cases is 

 largely found in both the augite and feldspar. 



The iron oxide is always in the form of menaccanite, which in every 

 case is altered to a large degTce to leucoxene, some specimens .showing 

 beautiful alternating bars of menaccanite and leucoxene. 



The area in Sees. 20, 29, and 30, T. 47 N., B. 43 W., Michigan.— 

 Between Sees. 20 and 29, but mostly in Sec. 29, is a continuous range of 

 greenstone which extends from the valley of the Presque isle for more than 

 a mile westward. Here there is a break, and again in Sec. 30 this green- 

 stone ridge appears. As examined on the ground it has the appearance of 

 an interbedded floAV. That it was really contemporaneous with the forma- 

 tiolx of the series is further indicated by the fact that at its northern base, 

 in Sec. 20, a jasper-conglomerate is found which is largely composed of 

 debris, like the material of the greenstone. (See pp. 369-370.) The iron- 

 bearing formation in Sec. 30 is found upon the south side of the greenstone 

 ridge, and upon the north side there is also a heavil}' ferruginous rock. In 

 Sees. 20 and 29 the iron belt is on the north side, but whether a similar belt 

 is on the south side has not been proved by exploration, but it probably 

 exists there. 



Petrographically, this rock also has all the characteristics of a surface 

 flow. It is a much altered augite-por})hyrite. It varies a good deal in 

 coarseness of strain and in decree of alteration, but the original minerals 

 are found with sufficient frequency, and the secondary minerals are so imi- 



