250 Dr T. THOMSON'S Account of the 



is much softer than corundum. The analysis was conducted by 

 heating the pounded mineral with carbonate of soda, in a plati- 

 num crucible. Much of the success depends upon the fineness 

 of the powder to which the hyacinth is reduced. The fused 

 mass was softened by water, and dissolved in muriatic acid. The 

 portion not taken up by the muriatic acid, was again heated 

 with a new portion of carbonate of soda, and the solution in mu- 

 riatic acid repeated. A third heating with carbonate of soda, 

 and digestion in muriatic acid, furnished a complete solution of 

 the whole mineral. The rest of the analysis was obvious and 

 easy. The constituents were found to be 



Silica, . . . 33.32 



Zirconia, . . 66.00 with a trace of iron. 



99.32 



The specific gravity of the crystals analysed was 4.6811. 

 It is plain from this analysis, that hyacinth is a sesquisilicate 

 of zirconia, or a compound of 



1-4 atom silica, 3 



1 atom zirconia, .... 6 



9 



5. Chrysoberyl from Brazil. 



Mineralogists are aware, that two different analyses of this mi- 

 neral have been laid before the public, within these few years ; 

 one by ARFVEDSON, and another by Mr SEYBEET. 



