Chemical Examination of American Minerals. 73 



It would appear from the analyses of the ceylanite from 

 Ceylon, by MM. Collet Descotils and Laugier, that its con- 

 stituents differ a good deal from those of the American miner- 

 al. This may be seen from the following table, 



Silica, - - 2 2 



Alumina, - - 68 65 



Magnesia, - 12 13 



Oxide of iron, 16 16*5 with a trace of manganese. 



98* 96-5f 



The lime in the American ceylanites is probably derived 

 from the calcareous spar in which the mineral was crystal- 

 ized. There is a smaller quantity of alumina, and a greater 

 of magnesia in the American, than in that of Ceylon. There 

 is also a considerable difference in the proportion of oxide 

 of iron, which each specimen contains. 



The spinell (if we consider the silica and iron as acciden- 

 tal) is obviously a compound of, 



1 atom magnesia, _ _ _ . _ 2*5 



6 atoms alumina, _____ 13.5 



16-0 



This is also the proportion of the magnesia to the alumina, 

 in the Ceylon variety. But the American ceylanite con- 

 tains only, 



1 atom magnesia, _ - - - 2-6 



4 atoms alumina, _ - . -9 



11-5 



* Collet Descotils, Ann. de Chim. xxxiii. 11. 

 t Laugier, Ann. de Chim. et de Phys. xxvii. 313. 

 Vol. III. 10 



