1824.] Analyses of Chrysoberyls from Hacldam and Brazil. 427 



Article VI. 



Analyses of the Chrysoberyls from Haddam and Brazil. By Mr. 



H. Seybert * 



In the summer of 1823, I visited Haddam, in the State of 

 Connecticut. Among the various substances there collected 

 was the Chrysoberyl, a mineral much esteemed on account of 

 its rarity. It occurs disseminated in a coarse grained granite, 

 in which the predominant ingredient is a white feldspar, which 

 Prof. Berzelius regards as Albite, perfectly resembling that of 

 Finbo. In the same granite this celebrated chemist observed 

 the Columbitc.-X It is also associated with greyish quartz, man- 

 ganesian garnet of a fine blood red colour, and a yellow granu- 

 lar substance, which some mineralogists supposed to be a variety 

 of the cymophane ; but from its inferior hardness and general 

 chemical composition, I recognised it to be common beryl. 



For the earliest chemical information concerning the chryso- 

 beryl, we are indebted to Prof. Klaproth. He published his 

 analysis of it in 1795,Jand gave the following constituents of it, 

 viz. alumina, 71*50; lime, 6; oxide of iron, 1*50; silica, 18; 

 loss, 3. Berzelius presented us with a formula founded on this 

 composition ; § but from his experiments with the blowpipe he 

 was led to conclude that it contained no lime, and that it was a 

 subsilicate of alumina. || In this he was apparently confirmed by 

 Prof. Thomson,** who quotes Klaproth's analysis, and states that 

 he examined the mineral some years ago, but having accidentally 

 lost his results, he was unable to publish them. He observes, 

 however, that the only constituents he found were alumina, 

 silica, and oxide of iron. When I was about to prepare the 

 communication which I now have the honour to lay before the 

 Society, a more recent analysis of the chrysoberyl of Brazil, by 

 M. Augustus Arfwedson, was observed, by me, in Tilloch's 

 Philosophical Magazine.ft He confirmed the results of Prof. 

 Thomson, and considered the chemical composition of this sub- 

 stance to be — silica, 18*73; and alumina, 81*43, with a trace of 

 oxide of iron. 



The cymophane, from Haddam, was sent to M. Hauy by the 

 late Dr. Bruce, in 1810, to have his opinion concerning its 



* Extracted from the second volume, New Series, of the Transactions of the Ameri- 

 can Philosophical Society, Philadelphia. 



+ Essai dc l'Emploi du Chalumeau, p. 243. 



J I'eitrage, vol. i. p. 97. 



\ Systeme de Mincralogie, p. 219, — C 4 S + 18 A 4 S. 



|| Essai de l'Emploi du Chalumeau, p. 8S5. 

 ■" Thomson**) Chemistry, vol. iii. p. 213. 

 •t + No. for November, 1823, p. 357. 



