Prof. B. Siiliman on some American Minerals. 452 



phorus. The reactions for silica, alumina, lime, iron and pot- 

 ash are satisfactory. It is not acted on by strong acids ; even 

 by long-continued Jboiling with Nordhausen sulphuric acid, 

 very imperfect decomposition was eifected. 



Fused with carbonate of baryta, a qualitative analysis gave 

 reactions for silica, alumina, peroxide of iron, lime and potash, 

 with a trace of soda. 



I was unable, however, with the most exact care, to con- 

 firm Dr. Smith's observation of the existence of zirconia — 

 probably a larger portion of the mineral might give a different 

 result. 



Dr. Smith gives the following as an approximate result of 

 the constitution of the emerylite from several analyses made 

 by himself: — 



Silica 30-0 



Alumina 50*0 



Zirconia 4*0 



Lime ISO 



Oxide of iron, manganese and potash . 3*0 



100-0 



- This analysis gives the ratio 4810^, eAlt)^, 3RO=3RO, 

 Si03+3(Aft)3jZW)2Si03, which gives the following re- 

 sult: — 



4 atoms Silica . . 2309-24 = 31-93 per cent. 

 6 ... Alumina . 3854-00 53-30 

 3 ... Lime . . 1068-06 14-77 



7231-30 100-00 



As however the mineral contains water and the analysis is 

 confessedly only approximate, this formula cannot be regarded 

 as entirely correct ; but it will be found useful in connexion 

 with the results which follow. 



The mineral which most closely approaches Smith's eme- 

 rylite, as far as our observations authorize us to form an opi- 

 nion, is the next in order, and marked in our analyses " A." 



A. This mineral is from Village Green, in the town of 

 Aston, Chester County, Pennsylvania, and was sent to me by 

 Mr. L. White Williams of West Chester, to whom mineralo- 

 gists are much indebted for bringing to light many interesting 

 things. It is associated with corundum, and occurs in con- 

 siderable masses; and so much resembling common mica, as 

 to have escaped notice until Dr. Smith's observations on 

 emerylite called my attention to the minerals associated with 

 the American corundums. Form, like mica, apparently hexa- 



2 G2 



