90 



ECONOMIC GEOLOGY. 



two great areas of porphyritic gneiss. Those who search for this min- 

 eral will find that the valuable deposits of mica are to be found chiefly 

 within this fibrolite area as delineated upon the map, corresponding with 

 that of the feldspar. 



Quarries for mining mica have been opened in the following localities : 

 In Grafton, the oldest and best known establishment is that of the Rug- 

 gles company, upon Isinglass hill. About 1840 they obtained some 600 

 or 700 pounds annually, valued at ^1,500. In 1869 they marketed 75 

 boxes of 350 pounds each, worth from $2.15 to ^2.50 per pound. This 

 makes a total of 26,250 pounds, worth perhaps $60,000. In January, 

 1877, the Ruggles mine is said to have shipped 3,600 pounds of mica, 

 selling for $2 per pound. They employed, in 1869, 12 men for seven 

 months of the year. Within two or three years the price of mica has 

 increased, and hence the business has been much stimulated. Grafton 

 now has six openings, which are all worked. Mellen's quarry is about 700 

 feet above the valley, to the north of the Ruggles mine. There are six 

 or eight places where excavations have been made. Martin & Page are 

 at work energetically, near the top of Alger or Beryl hill. This is the 

 locality where the largest known beryl was once on exhibition. These 

 parties have worked here for two years. Another place is opened by 

 Kilton & Sargent. On Hoyt hill in Orange is the Worcester mine. The 

 vein shows for 400 or 500 feet near the hill-top, and its maximum width 

 is 100 feet. Five men were employed here at the time of my visit. The 

 largest plate of mica obtained here is 8 inches square. There are two 

 other mines on the east side of the railroad in Grafton. There are others, 

 in Alexandria, New Hampton, Wilmot, Marlborough, Acworth, Alstead, 

 Groton, and Springfield. The Alstead quarry has been worked intermit- 

 tently the past thirty years by Mr. James Bowers, who sold in 1840 one 

 thousand dollars' worth to the Boston market. His quarry is on Beryl 

 hill, a famous locality for the latter mineral. On Hall's farm in Groton 

 arc unusually large plates of mica, where no mining has been done. The 

 Springfield locality has furnished beautiful and large tourmalines. 



Those who drive about Springfield, Grafton, Orange, etc., cannot fail to 

 see these veins on the hill-tops, whitening their crests and sides. The 

 vein on Hoyt hill, Orange, is quite conspicuous on the right-hand side, 

 as the cars near the summit from the south. Aaron's ledge in Spring- 



