WARREX AND PALACHE. — QUIXCV PEGMATITES. 129 



ing them, they are believed to be closely connected in their manner of 

 origin with the seams and veinlets occurring elsewhere in the granite 

 which are rich in riebeckite. The formation of these appears to be 

 connected with a period of movement attendeti by fracturing of the 

 granite and followed by a heading up of the fractures with granitic 

 material. (See general discu.s.sion at the end of Part I.) 



3rd. Three masses of pegmatite, pipe-like in form, one located in 

 Hallou's and the other two in Fallon's quarry, both (juarries being clo.se 

 together on the south central jxjrtion of N(jrth Common Hill, (^uincy. 

 These pipes are, up to date, the only im])ortant pegmatites of the 

 Quincy area and are the special subject of this paper. 



Occasional small patches of coarser texture than the granite occur in 

 several places in the area. Quite recently several have been found a 

 little to the east of the Balluu (juarry and just west of the Hardwick 

 quarry. They are interesting because of a considerable content of 

 molybdenite segregated about their margins. 



The Pegmatite of the Ballou Quarry, North Common Hill, 



QUINCY. 



The pegmatite in the Ballou ([uarry was first brought to the atten- 

 tion of mineralogists in l.s'.io, at which time it was examined by Dr. 

 Palache. In 1 *.>(»« a short description of it was published by Dr. Dale 

 (Bull. r. S. (i. S., No. 45:1 p. 4'J). Several handsome .sj)ecimens were 

 cut from it and polished by Mr. F. Wesley Fuller of West Quincy, one 

 of the finest, a complete section, now in the mineralogical collection of 

 Harvard University, being reproduced in Plate 1, Figure 12. 



The pegmatite was encountered at a depth of something like KK) feet, 

 and its downward extension, covered by slide material, still remains 

 in the bottom of the i^uarry. Its position is nearly vertical. Some 

 twenty feet of it have been removed, and while its depth is of course 

 largely conjectural, it seems .safe to assume that it is at least 40 or 50 feet. 

 Its form is that of a pipe, in places nearly cylindrical and again rudely 

 lenticular in cross-section with small, irregular branches. It is always 

 concentric in structure and sometimes shows an indistinct radial 

 arrangement of its minerals from the margin inward. Its three shells 

 or zones, although (juite irregular in outline and width and intimately 

 blended where they i)ass int<j one another, are nevertheless fairly dis- 

 tinct ; likewise the contiict with the granite is blended although the 

 change fnjm one to the other is sudden. The outer zone is chartlc- 

 terized by being considerably darker in color than the granite about 

 it. It is much heavier on one side of the pipe than the other. Its 



