418 THE I'ENOKEE IRON BEARIJfG SERIES. 



and the sections are then made u\} mostly of cldorite and calcite, with some 

 quartz, iu Avliich the particles of ])layioelase are set. 



In nearh" all of the rocks of the several areas of this division are por- 

 phyritic crystals of feldspar, which is the only mineral that occurs in two 

 generations. They are -sery lunnerous in the coarser grained varieties of 

 the area, but are altogether alisent in the glassy varieties. This porpli}^- 

 ritic feldspar is generall}' greath' altered and its exact nature can not be deter- 

 mined, but the double angles measured by Pumpelly's method indicate that 

 it is of tlie same character as the feldspar of the matrix. Its decomposition 

 products are tlie same as the feldspar of the backgi'ound; that is, smarag- 

 dite, chlorite, epidote, and kaolinite. The rocks of the division are always 

 amygdaloidal, with tlie exception of tlie exposures in the north part of Sec. 

 15. The amygdules are at times very numerous and frecjuently of quite 

 large size. They are generally of an elong-ated oval sluipe, the longer axes 

 of which are jjarallel and probably indicate flowage in this direction. The 

 tillin"' of the ann-gdules is one oi- more of the minerals chlorite, calcite, 

 epidote, or quartz, the latter usually being, when present, chalcedony. 

 Chlorite and calcite are the most plentiful minerals, tlie two frequently 

 occurring together iu the same amygdule in concentric belts. The chlorite 

 is always of a green iionpolarizing variety, or that giving steel-blue interfer- 

 ence colors. Often within the chlorite have developed large areas of epidote. 

 By comparing the above descriptions \\'ith those of the pebbles and certain 

 of the matrices of the greeiistone-coiiglomerates, it will be seen that there 

 is a remarkable likeness between the various phases of these eruptives and 

 the conglomerates, with the exception that in the conglomerates no diabase- 

 porphyry phase is found. The resemblance between these tine grained 

 eruptives and the greenstone-conglomerates is still further emphasized by 

 veins whicli cut tlicm, tliese being composed al times of intricately inter- 

 locking (piartz, chlorite, and epidote; that is, these sparse veins are almost 

 precisely like the liai'kgrouiid which contains the apparent fragments of 

 some of the rocks wliich liave Ix'eii classified with the greenstone-conglom- 

 erates. Whether these locks really belong there, that is, whether these 

 apparent fragments are really genuine or not, is uncertain. If the more 



