460 Prof. B. Silliman o« some American Minerals. 



^-^C Silica' V'^?«"/^ . . 0-292 = 37-C53 per cent. T^ 

 Alumina .... 0'4<84< 62-4.11 



0-776 100-064. 



Required. 



2 atoms Silica . . . 1154.-62 = Si03 37-47 



3 atoms Alumina . . 1 927*00 = Art)3 62-53 



This result gives then exactly the formula of kyanite, viz. 

 2A1X)^ 3Si03. The analyses of Staff and Norton give also 

 the same result*. 



We can therefore have no longer any hesitation in referring 

 Sillimanite to kyanite, as originally suggested by Haidingerf. 



Biicholzite is a name given by Brandes to a silicate of alu- 

 mina from Tyrol, which occurs in compact masses of a finely 

 fibrous structure and hardness equal to kyanite. Thomson 

 has also analysed a mineral from Chester County, Pennsyl- 

 vania, well-known to collectors, and has referred it to Buchol- 

 zitej. Being in possession of authentic specimens of the 

 Chester mineral, I have analysed it with the following result. 

 Quantity taken, 0*561 grm. Found — 



Another samole. 

 35-96 * 



0-5568 99-26 



This also will give us the same formula as kyanite. The 

 mineral being less pure than Sillimanite, cannot be expected 

 to furnish results as accurate as the former analysis. Prof. 

 Shepard in his System expresses the opinion that Bucholzite, 

 and Sillimanite were the same species. 



There is also found at Brandywine Springs, Delaware, a 

 mineral which has been extensively circulated under the name 

 of both Bucholzite and fibrolite. A specimen from this locality 



* In Prof. Norton's analysis, which was made in Yale College Labora- 

 tory, the excess of 2*73 was owing undoubtedly to aluininate of potash 

 which remained with the alumina after separating the peroxide of iron by 

 caustic potash. Subtracting this sum from the sum of alumina and per- 

 oxide of iron, we have 62'30 per cent, alumina and peroxide of iron, which 

 is almost exactly the quantity required by theory, and I have corrected the 

 analysis accordingly with the consent of Prof. Norton. That analysis was 

 made on the Sillimanite from Fairfield, New York. 



-|- In his translation of Mohs, vol. iii. 154. 



X Erdmann appears also to have made his analysis on the mineral from 

 tlie same locality. 



