THE CHESTER EMERY BED. 139 



The elevation of the ui)i)er outcrop of this bed above the immediate base of the 

 mountain is 750 feet. There are remarkable rounded masses of pure emery 3 feet in 

 diameter in this bed entirely invested with a coat of rose-colored margarite and a 

 thick layer of bright green chloritoid, the investing coat being from half an inch to 2 

 inches in thickness. It is found extremely dillicult to break uj) these masses of solid 

 emery, drilling holes in them being very slow and laborious, and no grip can be had 

 on their rounded sides by the sledge. A heavy drop liammer will be reijuired to break 

 them to pieces, or they may be cracked by fire if heat does not injure the emery. 



The first of the two sections given by Dr. Jackson and quoted aljove 

 refers to the old mine on the brook between the two mountains. 



The talc on the east has a thickness of from 5 to 15 feet. Much of 

 it is very pure, lightish-green, schistose talc. Much of it also carries dis- 

 seminated dolomite, often removed and leaving rusty holes. In places it is 

 a dark leek-gi-een, compact talc. 



Scattered through the talc are remnants, up to a foot in diameter, of 

 the serpentine from which the talc has doubtless been derived. These 

 nodules are rounded and pass outwardly by gradual transition into the talc, 

 and veins of the latter mineral also penetrate the serpentine. Large masses of 

 foliated talc could be obtained pure, but of inferior color — a very pale gi-een. 



The next band upon Dr. Jackson's section, "chlorite slate," is the usual 

 chloritic or coruudophilitic "fringe rock," which is here specially well 

 developed upon the eastern side (where it contains the oligoclase bed next 

 described) as well as upon the western. 



The corundophilite, in plates often 20°"° broad, is placed with consid- 

 erable regularity at right angles to its planes of contact with the oligoclase 

 in layers which reach 40'°"' thickness on each side of the latter. It often pen- 

 etrates the emery vein in sheets, filling fissures, and thus often inclosing on 

 all sides blocks of the ore, and in cracks not wholly filled develops excellent 

 crystals, upon which rest margarite in the finest foliated sheets and diaspora 

 in thick masses of interlaced blades and in separate crystals of great per- 

 fection associated with fine needles of rutile. The corundophilite is further 

 disseminated more or less through the mass of the magnetite-emery aggre- 

 gate, and where this aggregate lessens in quantity its place is taken by a 

 white to pink colored granular margarite, forming a schistose rock, for which 

 Professor Shepard proposes the name corundophilite-schist.' 



Where the corundophilite wholly disappears there results an interesting 



'Am. Jour. Soi.. 2d series, Vol. XLVI, 1868, p. 257. 



