Elements of Mineralogy. 



black frothy flag. That of Brazil forms otl* 

 ly a brittle fcoria. Of the ufual fluxes, bo- 

 rax diflblves them beft, microcofmic fait and 

 mineral alkali partially. 



The proportion of their conftituent prin- 

 ciples is thus exhibited by Mr Bergman : 



Tourmaline of TyroL 



Argill, - 42 



Silex, ~ 40 



Calcareous Earth, - 12 



Iron, - 6 



100 



Tourmaline of Ceylon. 



Argill, - 39 



Silex, - 37 



Calcareous Earth, - 15 



Iron, - 9 



IOQ 



Tourmaline of Brazil. 



Argill, - 50 



Silex, - - 34 



Calcareous Earth, - - 1 1 



Iron, - - * 5 



100 

 SPECIES XVIII. 



