^of Boston and its Vicinity 



It is moderately hard, passing to soft. 

 The fracture is from fine grained uneven to earlhy 

 specimens show a slightly slaty structure. 

 It is brittle. 



It is easily frangible. 



The fragments are indeterminately angular, and not 



larly sharp edged. 

 Its specifick gravity is about S,88 



159 



some 



partica- 



Chymical Characters, 



Before the blowpipe it melts into an opaque, semi-vitreous 

 Inass, which appears porous when broken. 



Geological Situation and Localities, 



o 



It occurs in beds inPetrosil^x at Milton, and forms the basis of 

 Amygdaloid at Brighton, Hingham, Newton, &c. and it is found 

 Jilso in rounded fragments at Needham, Newton, Brighton, &c. 



Memarlca. 



This mineral sometimes much resembles ferruginous clay, and 

 is intermediate between Clay and Basalt. It is very liable to de- 



and when it for 



basis of Amygdaloid, by 



leaves tbe imbedded minerals project- 



dergoing this change, it 



ing, or they fall out and leave the Wacke cellular. 



.J 



* 



