THE CHESTER EMERY BED. 137 



suddenly and then more grudually, to 12 feet, and appears again in the 

 river in an isolated rock with a somewhat greater width. 



The customary "fringe rock" (c) borders the vein on both sides from 

 an inch to a foot wide, the width being rudely proportioned to the width of 

 the emery vein. It is a soft schist, made up wholly of biotite. 



The emery vein is a chloritic magnetite containing in abundance 

 bi'onze-colored grains of emery, and, along the borders of the thicker portion 

 of tlie main vein and of the eastern vein, a considerable (juantity of brown- 

 black tourmaline in delicate stellate forms (e). 



This extreme contortion of the amphibolite is rare in the region, and I 

 may call to mind that, following the line of strike across the river from tliis 

 point, one comes directly upon the line of junction of the serpentine (which 

 has replaced the amphibolite) and the sericite-schist, and that the latter is 

 also contorted to an equally extreme degree. 



From the outcrop upon the river bank one follows the vein southward 

 up through a notch in the mountain, where, about 800 feet south, it has been 

 opened and some iron ore taken out, and then up along the eastern sloj^e 

 of the mountain, just under the crest, to the new mine, about a mile north 

 of the village, where alone work was in progress in 1883. 



The part of the vein rich in emery was about 1 to 3 feet wide Avhere I 

 saw it, and the corundum was regularly disseminated porpln-ritically in 

 rich bronze-colored crystals 5-15°"" across, affording a very rich ore. The 

 soft, green chloritic "fringe rock" was developed in great force and cuts 

 the emery bed in the bottom of the opening as a heavv horizontal 

 cross-vein. It was filled with bright fresh cubes of pyrite and crystals of 

 tourmaline 10-30'"™ long and ■2-3™" in diameter, which were all regular 

 hexagonal prisms, with rather dull unstriated sides. They are often radiated 

 and fasciculate. 



With a lens slides of the rock show wavy l)ands of a pale-salmon color, 

 which alternate with bands and lenticular patches of bright green. The 

 former are very fine fibrous, and show the aggregate polarization of talc. 

 The latter is in coarser scales, often radiate, and they polarize from green to 

 black. They have low absoi'irtion and pleochroism: c = pale blue-green; 

 b = same; a = bright yellow; extinction inclined 8° from the cleavage. 



Magnetite is aljundant; also deep-brown grains of chromite, the former 

 often interlaminated with chlorite. The tourmaline is in sharp hexagons; 



