46 Chemical 'Examination of American Minerals. 



The dark-green opaque grains in the rock, which accom- 

 panied the xanthite, were mostly rounded ; though some had 

 the appearance of crystalization, and seemed to approach to 

 9 four-sided flat prism, more closely than to any other shape. 

 Very easily frangible. 



The hardness could not be determined, as the grains broke 

 in pieces before the point of the knife, when an attempt was 

 made to scratch them. Opaque. 

 Specific gravity 3-223. 

 The constituents were. 



Silica, - - _ . . 24-72 



Magnesia, ----- 26-60 



Peroxide of iron, - _ - - 22*26 



Lime, . . - - - 21-60 



Alumina, ----- 3-60 



98-78 



This approaches, 



5 atoms disilicate of magnesia, 



3 atoms disilicate of lime, 



2 atoms disilicate of iron, 



I atom disilicate of alumina. 

 It is obvious from this analysis that the mineral is not am- 

 phibole. It is probably also new. But the small quantity 

 in my possession did not admit of an accurate description. 



Note. By some of our mineralogists, the xanthite of Dr. 

 Thomson has been considered as the pyrallolite of Nor- 

 denskiold, a mineral which is very indifferently described in 

 the books. 



The small dark-green substance associated with it has been 

 called pargasite, which is a mere variety of amphibole ; but 

 Dr. Thomson's analysis would seem to establish the Amity 

 mineral as a peculiar species. It should, however, be re-ex- 

 amined, as Dr. Thomson operated on imperfect specimens. 



