RE-EXAMINATION OF AMERICAN MINERALS. 131 



We obtained 



Oxygen. 



Oxide of nickel 56.82 12.10 



Magnesia 1.68 .67 



Carbonic acid 11.63 8.46 



Water 29.87 26.56 



which gives the formula Ni 3 C+6H. 



Atoms. At. weight. Percent. Oxygen ratio. 



Oxide of nickel 3 1408 59.72 3 



Carbonic acid 1 275 11.66 2 



Water 6 675 28.62 6 



We would prefer expressing its formula by an atom of car- 

 bonate of nickel plus two atoms of the hydrated oxide of nickel. 

 This is rendered probable from the fact that whenever it is 

 attempted to form a carbonate of the protoxide of nickel by 

 precipitating a protosalt with an alkaline carbonate, a carbon- 

 ate is obtained containing a certain amount of the hydrated 

 oxide. For these reasons we would express emerald nickel 

 by Ni C+2(]Sri H 3 ). It is without question a distinct species and 

 a most beautiful and interesting mineral, both from the richness 

 of its color and its association with chromic iron. 



Since completing our examinations of this mineral we have 

 observed an analysis of a mineral called emerald nickel by 

 Mr. T. H. Garrett. The mineral examined was of a very 

 impure description, and was supposed by the analyst to be a 

 mixture of emerald nickel, meerschaum, and augite ; of course 

 it is impossible to furnish any correct idea of the composition 

 of pure emerald nickel from results on such impure specimens. 

 This mineral is often associated more or less intimately with a 

 nickel serpentine or gymnite; but with an abundance of the 

 mineral to select from, a hydrous carbonate of nickel can be 

 obtained of a uniform composition. A quarter of an ounce 

 of selected fragments sent by Mr. L. White Williams furnished 

 us with about one gramme of the pure mineral. 



27. Danburite. 



This mineral has as yet been found in only one locality— 

 Danbury, Conn. It was first described by Prof. C. U. Shepard,* 

 and considered by him a hydrated silicate of lime and potash. 

 Still later it was examined by Dr. H. Erni,f and boracic acid 



* Amer. Jour. Science and Arts, 1st series, xxxv, 129. 

 tAmer. Jour. Science and Arts, 2d series, ix, 286. 



