Constituents of various Minerals. 255 



The result of the analysis was as follows : 



Silica, ....... 55.908 



Magnesia, .... 27.068 



Lime, 14.632 



Alumina, 1.820 



Protoxide of iron, . . 6.528 



105.956 



I believe the excess in this analysis to be chiefly owing to the 

 magnesia, which had in all likelihood been mixed with a por- 

 tion of the double carbonate of potash and magnesia : For the 

 method which I employ to analyse minerals containing lime, 

 magnesia and alumina, is to throw down the alumina and oxide 

 of iron by bicarbonate of potash. The liquid thus freed from 

 alumina, &c. is neutralised by muriatic acid, and the lime thrown 

 down by oxalate of ammonia. The liquid thus freed from lime, 

 is heated to the boiling temperature, and gradually mixed with 

 carbonate of soda, while kept boiling briskly, to throw down the 

 magnesia. If the carbonate of soda be added too rapidly, or if 

 the liquid be not made to boil briskly, the compound salt is apt 

 to make its appearance, in which case, it is exceedingly difficult 

 to get the magnesia in a state of purity. 



Whoever will take the trouble to compare the preceding ana- 

 lysis of amianthus with the numerous analyses of amphibole by 

 BONSDORF, in the Memoirs of the Stockholm Academy for 1821, 

 p. 192, will see at once that it is merely a variety of that very 

 proteus-looking mineral. 



One of the most common varieties of amphibole consists of 



3 MS 2 + CS 3 ; 



