Prof. B. SilHman on some American Minerals, 461 



furnished me the following results, viz. quantity taken, r0675 

 grm. Found — 



Silica . . . 0-386 = 36*159 per cent. 

 Alumina . . 0679 63-525 



1-065 99-684. 



This is evidently identical with kyanite. Minute traces of 

 iron and manganese, which are found in both the above, are 

 regarded as of no importance in the result, being mere impu- 

 rities*. 



Fibrolite of Bournon. — This mineral was first distinguished 

 by Count Bournon, who detected it among the associated 

 minerals of corundum from India and from China. The 

 name has reference to its fibrous character. It was analysed 

 by Chevenix, who found — 



Silica 38-00 



Alumina 58'25 



96-25 .shtav 



Even upon so imperfect an analysis, there has been no he- 

 sitation with most writers in referring it to kyanite. Having 

 a specimen of this mineral from Count Bournon at my dis- 

 posal, I have analysed itf. It yielded on 0*427 grm. taken — 



Silica . . . . 01 55 1 = 36-309 per cent. 



Alumina . . . 0*2665 62*415 

 Magnesia . . 0*0030 0-702 '"ai: uei^:. 



0*4246 99*426 



The results just given leave it no longer possible for us to se- 

 parate Slllimanite, Bucholzite, and fibrolite from kyanite. The 

 hardness of Sillimanite proves also to possess the same inequa- 

 lity on different faces which is found in kyanite. The cleavage 

 face is much softer than the angle or side of the prism, so as 



* It may be objected to the conclusion that Bucholzite is identical with 

 kyanite that I have not analysed a specimen of the original mineral. This 

 I should have done could I have procured one in time for my present 

 purpose. The Chester mineral here analysed was received by Baron Le- 

 derer from Dr. Nuttall, and so far as I can learn, no one questions that the 

 mineral from that locality corresponds entirely with the Bucholzite of 

 Brandes. I am convinced that those chemists who have obtained so high 

 a per-centage of silica in their analyses of disthene minerals, had not taken 

 the precaution to employ the aid of caustic potash, added to the assay 

 during fusion, as recommended by Berzelius ; and that if they had re-ana- 

 lysed their silica they would invariably in cases where the amount exceeded 

 38 per cent., have found in it a portion of alumina. 



t The specimen referred to was taken from the collection of Col. Gibbs 

 (now in Yale College), and was received by him from Count Bournon in a 

 large collection of gems which this gentleman furnished to Col, Gibbs.. ^jj^ 



