THE CHESTER EMERY BED. 123 



Emery Mine. 



The discovery of this mine so recently as the autumn of 1864 within the houiul- 

 aries of the State of Massachusetts, where so much attention has been given to 

 mineralogy and geology, seems somewhat singular; the more so, perhaps, as its occur- 

 rence is so near the machine shops and armoiies iu which the consumption of emery 

 is very considerable. Among tlie reasons of its delayed discovery may be adduced 

 its situation in a mountainous and thiuly inhabited section, which nntil recently has 

 attracted but little scientihc or economic notice. Emery, moreover, being itself rich 

 in iron and largely associated with magnetic iron ore (magnetite), is extremely liable 

 to be confounded with the latter substance, and this was the case with it at Chester, 

 whence about 1,000 tons were raised for iron making before its true nature was ascer- 

 tained. The discovery would probably have been still longer deferred but for the 

 happy suggestion of Prof. J. Lawrence Smith,' that the occurrence of the margarite 

 at Chester should lead to a direct search for emery, this mineral being one of the 

 invariable concomitants of that highly important substance. This suggestion was at 

 once successfully acted upon by Dr. Lucas and N. C. Sawyer, esq. 



The mine is situated nearly in the center of the Green Mountain chain as it 

 traverses the western border of the State, at a point not far from halfway between 

 the Connecticut and Hudson rivers. It is included in the metamorphic series of rocks, 

 here consisting of vast breadths of gneiss and mica-slate, with considerable inter- 

 polations of talcose slate and serpentine. The general direction of the stratification 

 is jST. 20° E. and S. 130° W., the relation to the horizon varying from vertical to a dip 

 of from 75° to 80°, sometimes east, sometimes west. 



The immediate vicinity of the mine jiresents a succession of lengthened rocky 

 swells with rather precipitous sides, having summits between 750 and 1,000 feet above 

 the level of the principal streams by which the hills are traversed. The longer axis 

 of the elevations generally coincides with the direction of the strata. 



The emery vein traverses in an unbroken line the crests of two of these adjoining 

 mountains and scarcely deviates as a whole from the magnetic meridian. Each moun- 

 tain is estimated to have a length of 2 miles, thus giving 1 miles extent to the metallif- 

 erous stratum, for such it may truly be called, consisting, as it does, so largely of the 

 metals iron and aluminium. The Westfleld Kiver, here a small stream of about 4 rods 

 in width, flows directly across the northern end of the vein, while a branch of the same 

 river, having half its size, separates the two moirntains and very nearly divides the 

 vein into two equal portions. The height of each mountain is estimated at 7.50 feet. 



The emery vein, whose average width may be taken as 4 feet, is situated near 

 the junction of the great gneiss formation constituting the western flank of the 

 mountains, with the mica-slate forming their eastern slope. To speak more exactly, 

 however, it lies Just within the gneiss, having throughout a layer of this rock from 

 4 to 10 feet iu thickness for its eastern wall. Nor does the mica-slate advance quite 

 up to this outside layer of the gneiss, but, in place thereof, an extensive intrusion of 



' To Dr. Smith we are indebted for tlie first scieutitic surrey of the emery mines of the Grerian 

 Archipelago and Asia Minor. 



