170 



Outlines of the Mineralogy and Geologj/ 



§ 



The streak is light greenish grey. 

 It is hartl. 



The fracture is fine grained uneven, and from small to large 

 imperfectly straight foliated ,with a twcfold obliquely intersectin 



cleavage, and tlie fractured surface is sometimes longitudinally 

 striated. 



I 



It is very tougb. 



It is very difficultly frangible. 



r 



The fragments are indeterminately angular, and rather blunt 

 edged. 



The specifick gi-avity is about 3.084. 



Chi/mical Character, 

 Before tbe blowpipe it melts into a dark green or black glass. 



Geological Situation and Localities. 



It occurs in rounded masses 



9 



Cambridge, Brighton, West 



Cambridge, Watertown, Dan vers, &c, and forms a constituent 



part of Greenstone, and Sienite. Tbe long acicular crystal 



are 



partially decomposed, and are found shooting 



gh crys 



of Feldspar, in some varieties of Sienite, at Charlestow 



iM** 



Subspecies IL—BasalticJc Bornblenie. 



Basaltic Hornbleade, Ckavdand, p. 336. Idem, Jameson, vol. i. p. S65, 

 Idem, dikirif p, 235. Basal tine, JCirwan, vol. ii. p. 219. 



JExtevnal Characters, 



Its colour is velvet black. 

 Its lustre is shining. 



-»■ 



