30 GEOLOGY OF OLD HAMPSHIRE C0U:NTY, MASS. 



and the same is true tliroughout Berkshire County/ I think it probable 

 that the rock was derived from an impure hmestone, but must leave its ori- 

 gin in doubt, because no lithological criteria can be found that will distin- 

 guish amphibolites derived from lavas or tuffs and those derived from 

 impure limestones. In the succeeding sections treating of the amphibolites, 

 to which reference may be made (see Chapter X), only those from the east 

 of the river in Leverett have shown distinct residual characteristics peculiar 

 to eruptives and comparable to those found in the altered eruptives of the 

 Baltimore (Maryland) area and of several foreign localities. 



RESTJIVIE. 



These oldest gneisses are coarse, often very coarse, often granitoid, 

 and the cleavage surfaces of the large microclines are strongly curved. 

 AUanite is very generally distributed, at times abundant. 



The chondrodite-phlogopite-limestones are characteristic. 



The upper gneisses, often strongly foliated, are marked by the universal 

 distribution of graphite, at times so abundant as to tempt mining, and by 

 the abundance of the peculiar blue quartz, of hornblende, and of iron rust. 

 Allanite is even more abundant here. 



' Professor Kemp haf recently called attention to the fact that similar black hornbleudic rocks 

 are constant attendants of the pre-Cambrian limestones of the Adirondacks, fringing the beds both 

 above and below. Geol. Moriah and Westport: Bull. N. V. State Museum, Vol. Ill, 1895, p. 329. 



