MINERALOGICAL NOTES. 155 



calcite, some titanite and titaniferous magnetite. The 

 orthoclase has inclusions of plagioclase and the plagioclase 

 in turn has inclusions of micro-zircons. There are also 

 numerous cubical crystals of iron pyrites in the section. 

 Other sections of these granite veins are seen to contain 

 some green hornblende and biotite with occasional patches 

 of chlorite and apatite crystals. The quartz biotite and 

 hornblende are usually developed near the contact and is 

 an indication that these granite veins arise from segrega- 

 tion of newly formed minerals in cracks and crevices of 

 the rock-mass in which they are found. 



This paper is the result of quite extended field work 

 during portions of several years and is part of a prelim- 

 inary report upon the geology of Essex County in behalf 

 of the Peabody Academy of Science. 



I wish to acknowledge my obligation to Dr. J. E. 

 Wolff, instructor in the petrographical laboratory at Har- 

 vard College, for much kind assistance and advice. 



Peabody Academy of Science, 

 Salem, Aug. 3, 1891. 



