138 GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



CO = black, £ = deep prussian-blue, witli black border. Sharply refringent 

 grains of titanite, with dark border surrouudiug them, occur in the chlorite. 

 The opening was otherwise poor in the usual accessory minerals of the vein, 

 only traces of margarite occurring. Here also a branch vein I'uns off to 

 the east and the mica-schist is greatly contorted. 



Going south toward the old mine in the valley, one passes, about a 

 third of the way on, the large abandoned Sackett mine, opened about 50 

 feet on the vein, which is here about 12 feet wide and has been extensively 

 worked for magnetite. The thin "fringe rock" can be seen attached to the 

 hornblende-schist on the west wall of the opening over a broad surface. 

 In the magnetite only a limited amount of emery is -vasible, and no other 

 minerals could be found. Dr. Jackson says: 



On the North Mountain the emery is more largely crystalline and less mixed with 

 magnetic iron; it is more like corundum, but still contains the combined protoxyd of 

 iron, characteristic of true emery. 



Three large beds of rich magnetic iron ore, distinct from the ore accompanying 

 the emery, occur, the ore yielding 54^ per cent of metallic iron. This ore is mined 

 and is smelted into bar iron by forge fires, and is also sold to mix with the hematites 

 and carbonates of iron at the Lenox and Stockbridge furnaces. 



The next opening on the vein is at the foot of Noi'th Mountain, north 

 of the Becket road and directly opposite to the main works. (See fig. 7, 

 p. 141.) Here, at the head of a small ra%a)ie, an adit was driven in 500 

 feet during 1893, and brought out a great quantit)^ of the fringe rock, filled 

 with beautiful rosettes of the hexagonal tourmaline. Of the further con- 

 tinuation of the vein across the brook and np the north face of South 

 Mountain Dr. Jackson writes as follows: 



The principal bed of emery is seen at the immediate base of the South Mountain, 

 where it is 4 feet wide and cuts through the mountain near its summit at an angle of 

 70° inclination, or dip, to the eastward. Its course is N. 20° B,, S. 20° W., and its 

 known extent 4 miles. Near the summit of the mountain the bed expands to more 

 than 10 feet in width, and in some places is even 17 feet wide. 



The alternations of rock in two sections are as follows, beginning to the eastward 

 [that is, at the top J : 



1. a, Mica-slate; h, 15 feet soapstoue or talcose rock; c, 2 feet crystallized talc; 

 d, talcose slate; e, 1 foot granular quartz ;/', chlorite slate; //, 4 feet emery ; h, chloritoid 

 and margarite; i. magnetic iron ore; .;, hornblende rock highly crystalline. 



2. a, Mica-slate; b, G feet magnetic iron ore; e, talcose slate; d, 6i feet magnetic 

 iron ore; e, chloric slate; /, hornblende rock, crystallized; g, 7 feet emery, chloritoid, 

 and margarite; /(, magnetic iron ore; i, horiiblciide rock. 



