46 EMERY MINE OF CHESTER, MASS. 



mountain to a breadth of nearly two hundred feet as it reaches 

 the terminus of the vein, in the bed of the Westfield Eiver. 



" The gneiss, more especially in the vicinity of the vein, is a 

 very peculiar rock. It abounds in thick seams of a coarse- 

 grained, very black and shining hornblende, and where this 

 is not found, it is much veined and penetrated by epidote. The 

 stratification is much contorted also ; and when the surface 

 of the formation happens to be weathered or water-worn, its 

 basseting edges strikingly resemble in color some of the ser- 

 pentine marbles. It is also noticeable that in it quartz is 

 every where singularly deficient. Traces of a white calcareous 

 spar (calcite) are now and then visible upon the joints of the 

 gneiss, with occasional specks of yellow copper, together with 

 malachite stains; but no corundum, emery, or magnetite par- 

 ticles have thus far been detected as constituents of the gneiss. 

 It is quite otherwise, however, with the talcy rock exterior 

 to the wall of gneiss ; for that formation in all its different 

 varieties of talcose slate, soapstone, chloritic aggregates (with 

 included seam of indianite), talcy dolomite, etc., which together 

 constitute the stratum separating the gneiss from the mica- 

 slate, contain here and there disseminated grains of either 

 emery, corundum, or magnetite ; but, like the gneiss again, are 

 strikingly free from quartz or uncombined silica in any of its 

 forms. Indeed, this generally abundant substance is altogether 

 wanting, not only in the emery vein, but in the talcose forma- 

 tions constituting its eastern boundary. 



" It makes its appearance, however, in abundance in the 

 mica-slate as soon as the talcose rocks are passed — showing 

 itself not only as the usual constituent of the slate, but in more 

 or less continuous seams, from a few inches thick up to above 

 six inches, and sometimes a foot, in width. Where the seams 

 are thin and discontinuous, the included masses thin out at 

 each end before disappearing, the sharp edges being curved in 

 opposite directions, so as to form frequent white patches upon 

 the surface of the rocks in the shape of the letter S." 



MINERALOGICAL CHARACTER AND COMPOSITION OF THE CHESTER 



EMERY. 



It resembles more nearly that from G-umuch-dagh (near 

 Ephesus) than any other that I know of. It is of a fine grain, 



