1921] NATURAL SCIENCES OF PHILADELPHIA 185 



crystals of apatite and zoisite. The last zone is composed of 

 coarsely matted reddish-brown biotite from four inches to four feet 

 thick containing many nodules of dark green fibrous actinolite and 

 large nodules and crystals of corundum. Beyond this lies the sax- 

 onite which for a distance of three to twelve feet contains a network 

 of veins of colorless, fibrous anthophylhte, — the asbestos for which 

 the pit was worked. 



The tourmaline, rutile, and allanite are characteristic of peg- 

 matitic assemblages, and in this case a pegmatitic facies probably 

 developed at the margin of the Pelham granite gneiss which reacted 

 with the saxonite to form the interesting series of contact minerals. 

 Beyond the contact zones siliceous solutions entered the fractured 

 saxonite and silicated the saxonite minerals to anthophylhte. 



Chester, Massachusetts: The Chester emery deposits have 

 been described by Jackson, ^^ Shepard,^' and Emerson. ^^ The 

 Chester emery deposits occur as a series of small disconnected len- 

 ses up to sixteen feet in thickness, but averaging four feet, between 

 the Chester hornblende schist and serpentine. The hornblende 

 schist is a dark-green to black foliated or ligniform epidotic quartz- 

 hornblepde schist considered by Emerson to be of sedimentary 

 origin. The hornblende schist is bordered at several places with 

 lenticular intrusive masses of serpentine. 



The emery vein consists of a mixture of chlorite and magnetite 

 containing in abundance bronze colored crystals of corundum, and 

 a considerable quantity of tourmaline in black crystals or stellated 

 aggregates. In passing from the hornblende schist to the serpen- 

 tine the following sequence is noted: hornblende schist, biotite layer, 

 chloritic band with tourmaline, emery vein with various minerals, 

 corundophilite zone, talc zone, and finally serpentine. The corun- 

 dophilite zone may be wholly replaced by a white to reddish, fine 

 grained saccharoidal oligoclase up to twelve inches in thickness. 



One of the most interesting sections is that of the mine at the 

 base of South Mountain. The serpentine on the east passes into 

 a zone of pure, light-green, schistose or massive talc, through 

 which are scattered remnants of serpentine from which the talc was 

 derived. The width of this zone varied from five to fifteen feet. 



»« Am. J. Sci. (2) 39: 87, 1865. _ 



^^ Charles U. Shepard, A description of the emery mine of Chester, Hampden 

 County, Mass., London, 1865. 



'^U. S. Geol. Surv. Bull., 597: 159-161, 1917. 



See also Earl V. Shannon, Am. Min., 4: 69-72, 1919. 



