20 



gular crystallization^f primitive trap and sienite, together 

 with the greater impurity of the felspar, and very com- 

 pounded nature of the hornblende and rutilite, indicate an 

 inferior purity of the solution, and, consequently, later pre- 

 cipitation of the crystallized mass. 



THIRD SPECIES. 

 NIGRINE. 



Nigi'in of Werner. 



EXTERNAL CHARACTERS. 



The colour is dark brownish black, passing into velvet 

 black. 



Is found in larger and smaller angular grains, and 

 pebbles. 



Externally, moderately glistening. Internally, principal 

 fracture is glistening; the transverse fracture moderately 

 glistening. 



Lustre, adamantine. 



The principal fracture is imperfectly foliated, with a 

 single cleavage; the transverse fracture is flat, and imper- 

 fectly conchoidal. 



The fragments are indeterminately angular, and sharp- 

 edged. 



Perfectly 



