226 



Scientific Geology. 



of baryta. On the most southern of the islands at Turner's Falls, 

 the gangue of the pyritous copper is a brecciated sandstone, the vein 

 crossing the regular strata ; though coinciding with them in direction. 

 That is, both run nearly north and south ; but while the slate dips 

 about 45° easterly, the vein dips westerly. It would seem as if the 

 intrusion of the copper ore had broken a portion of the sandstone 

 into fragments, and the materials had been partially melted, so that 

 on cooling, a chemical union took place between them and the walls 

 of the vein. On the edges of the sandstone strata, for several feet 

 and even rods, around this vein, may be seen numerous crystals of 

 lenticular carbonate of iron. (No. 240) 



All the veins of copper ore in the formation under consideration, 

 run in nearly the same direction, so far as I have examined them : 

 that is, nearly north and south ; indicating some common cause from 

 which they originated. 



The vein of pyritous and the green carbonate of copper, half a 

 mile below Turner's Falls in Greenfield, affords a good example, at 

 low water, of the passage of the vein through the trap and the sand- 

 stone. Although it has not been explored, veins of sulphate of bary- 

 ta, sometimes several inches wide, and accompanied by copper, may 

 be seen passing into both rocks. The trap is that variety denominated 

 toadstone; the base being apparently indurated clay. The red slaty 

 rock connected with the trap, may be regarded as a variety of slate, 

 sometimes a little micaceous. As nearly as I could determine, this 

 vein is perpendicular ; and as it passes northerly into a lofty hill of 

 trap, it might in that direction be advantageously explored. A few 

 hundred dollars laid out here, would probably determine the value of 

 the vein. 



I have put down a second copper vein on the map, a mile or two 

 south of the one just described. I did it on what I thought good au- 

 thority ; but subsequent examination has led me to doubt whether it 

 has an existence ; although I am aware how easy it is to overlook 

 such a locality without a guide. 



The copper ore in Granby,Ct. (called the Simsbury Mines,) ap- 

 pears so far as it has been explored, to be a bed lying entirely be- 

 tween layers of sandstone, which dip to the east a little more than 

 20°, and running between north and south, and northeast and south- 

 east. The red oxide is the principal ore, sometimes mixed with a 

 little of the green carbonate. The gangue appears to be gray sand- 

 stone. Since this mine has been reopened, about a thousand tons of 



