72 Chemical Examination of American Minerals. 



This approaches the constituents of the spinell, as deter- 

 mined long ago by Berzelius. He obtained, 



Silica, 5-48 



Alumina, ----- 7225 



Magnesia, ----- 14*03 



Oxide of iron, - - - - 4-26 



Undetermined matter, - _ - l«83 



98-45 



The American spinell contains a good deal more oxide of 

 iron than the SAedih. This was to be looked for, as its 

 color was much darker. 



I have got specimens of ceylanite both from Dr. Torrey 

 and Mr. Nuitall. They are all crystalized in regular octa- 

 hedrons. They are opaque, and the color is so dark a green, 

 that the crystal appears to the eye black. The rock in which 

 these crystals occur is calcareous spar. They are as hard 

 as the spinell, but very easily frangible. The crystals in 

 some of Mr. Nuttall's specimens, are above an inch in length. 

 Dr. Torrey's are smaller, but exceedingly pt-rfect. The spe- 

 cific gravity of one of the large crystals vvas 3-575. The 

 locality of these ceylanites is Amity, Orange County, in the 

 State of New- York. 



A careful analysis of one of the purest looking crystals 

 gave the following constituents, 



Silica, - . - - . 5-596 



Alumina, - - - - - Cl-788 



Magnesia, ----- 17-868 



Protoxide of iron, - - - - 1.0-564 



Lime, _ - - . . 2-804 



Water, - * - - - 0-980 



99-600 



