434 



Scientific Geology. 



in general a radiated structure, and sometimes invest calcareous spar. 

 (No, 1173.) A little below Turner's Falls in Gill, just at the mouth 

 of Fall River, on the east bank, is the best locality of this mineral with 

 which I am acquainted. More frequently the cavities are occupied 

 with earthy chlorite, and the specimens of this kind are very common 

 along the eastern side of the ranges of greenstone in the Connecticut 

 valley; as in Greenfield, Deerfield, South Hadley, Northampton, and 

 West Springfield. 



At the locality just referred to at the mouth of Fall River, occurs 

 the rare mineral chlorophoeite : which has not to my knowledge been 

 found in any other place on this side of the Atlantic. It is abundant 

 in the projecting mass of greenstone that appears at the junction of 

 the Connecticut and the small river just mentioned ; on the east bank 

 of the latter ; and the spot can hardly be mistaken by any one desir- 

 ous of finding it. This mineral, when the rock is first broken, is of 

 a dull green color : but after a few hours exposure it becomes nearly 

 black. After long exposure, however, some specimens assume a 

 dark brown color. For the most part the nodules, — often half an inch 

 and sometimes more than an inch in diameter, — exhibit a fibrous 

 structure, the fibres radiating from one or more centers in the same 

 nodule. The mineral is easily scratched with a knife and the pow- 

 der is of a dull green color. When fractured, however, it appears 

 brittle. Sometimes calcareous spar is enclosed within the chloropho- 

 ite : but very rarely are the nodules hollow. If I mistake not, in one 

 or two instances I have observed a foliated structure in specimens. 

 There seems little danger of exhausting this locality. The same rock 

 contains disseminated prehnite, chlorite, and pyritous copper. It is 

 however, but slightly amygdaloidal. Mr. Shepard has recently an- 

 nounced the existence of datholite in Middletown Ct. in a rock exact- 

 ly resembling that containing the chlorophoeite ; nor can I doubt but 

 this mineral will be found in Massachusetts. 



Prehnite has been found in the greenstone in the vicinity of Bos- 

 ton, particularly in Charlestown. But it is more common in the val- 

 ley of the Connecticut. Near the chlorophoeite locality just described, 

 on the Greenfield shore of the Connecticut, it is not uncommon in 

 amygdaloid. There its color is nearly white. In general it is more 

 common on the eastern side of the greenstone ridges, than on the 

 western ; for example, where Deerfield river cuts through a ridge of 

 this kind in Deerfield, and on the east side of the same ridge four or 

 five miles farther south, in a part of the town called Pine Nook : 



