142 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



mine, for a section of the imdergrouud work at the old mine south of the 

 mill, and a plan of the new opening directly opposite and north of the brook. 

 (See fig-. 7.) It will be seen that the magnetite-emery vein is not contin- 

 uous, but lies in sepai-ate lenticular masses or chimneys — "pots," as they 

 are locally called. 



Southerly the outcrop of the emery bed rises rapidly to the top of 

 South Moimtaiu and has been opened at several points. About 650 feet 

 south of the point where the road to the Slelvin mine crosses the bed an 

 opening shows chloritic magnetite, without visible emery and talc, with 

 brown spar on the east, pro%'ing that the talcose stratum is very persistent. 



At the Mehnn mine, the most southerly point to which the bed has been 

 traced, the ore has been removed in an open working about 130 feet on the 

 strike and 35 to 40 feet in depth, to the full width of the bed, which is 6J 

 feet wide at the north end and opens out for a distance of 33 feet to a width 

 of 16 feet, and then contracts again southward to a width of nearly 10 feet. 



The ore is mosth- a chloritic magnetite with few accessory minerals, 

 margarite of rare beauty being the only interesting occurrence. A little 

 tom-maline is present. The epidotic amphibolite appeai-s in a thin band on 

 the east of the emery bed, separating it from the sericite-schist farther east, 

 and on the west the same amphibolite adjoins the bed and makes up the 

 whole western half of the mountain. 



The soft chloritic "fringe rock" bounds the ore for a distance and then 

 runs behind a layer of hornblende 2 J inches thick. Farther south, at the 

 Bartholomew soapstone quarry in the noith of Blandford, and at the 

 Osborn soapstone quan-y, the same chloritic "fringe rock" occurs, and at 

 the latter place, adjoining the main soapstone bed on the west, a layer of 

 magnetite about 1 inch thick occurs, wliich I thought at one time to contain 

 emer}*, but I was not able to confirm this on further investigation. 



Taking, however, the known limits of the bed, there is "in sight" a 

 verv great quantity of magnetite and emery — extending a length of about 

 4 miles and a depth of about 750 feet above the water level of the brook, 

 and ha^•ing an estimated average thickness of 4 feet. Nevertheless, it must 

 be admitted that the exploitation of the deposit has been of much more 

 scientific than pecuniaiy profit, and that it has not reahzed the sanguine 

 expectations of the early promoters. 



