452 Warren — Pegmatite in the Granite of Quincy, Mass. 



nlar changes which resulted in the formation of the crocid- 

 olite and hornblende needles. Crystallization went on contem- 

 poraneously with the above process, although solution seems to 

 have slightly predominated at the end. Surface waters appar- 

 ently have had but little effect beyond a little kaolinization 

 of the feldspar and oxidation of the iron-bearing minerals. 



A closely similar pegmatite, except that the central pockets 

 were lacking, was found about live years ago in the JBallou 

 quarry, located a short distance to the north of the present 

 occurrence. In the Ballon quarry, the pegmatite had the form 

 of a nearly vertical pipe some 2 ft. in diameter and about 50 

 ft. deep. Many handsome polished blocks were made from 

 this at the time by Mr. F. Wesley Fuller. 



It is believed that a more extended study of these pegmatites 

 will furnish much valuable information regarding the chem- 

 ical composition of the minerals of the enclosing granite and 

 about other problems connected with the interesting riebeck- 

 ite-segirite rocks of the Quincy and Blue Hill area. 



Laboratory of Mineralogy and Petrology, 

 Massachusetts Inst, of Technology, 

 July, 1909. 



