158 Elements of Mineralogy, 



No acid has any effeft on it, except the 

 vitriolic; if diamond powder be triturated with 

 this acid, and evaporated nearly to drynefs, 

 the acid grows black and depofits pellicles, 

 which burn and are almoft entirely con- 

 fumed. 



In a heat fomewhat greater than that in 

 which lilver melts, diamond is intirely vola- 

 tilized and confumed ; it even produces a 

 flight flame and diminimes common air, juft 

 as phlogiftic fubftances do, and leaves a foot, 

 fo that the extraordinary conjecture of bir 

 Ifaac Newton, of its being an inflammable 

 fubftance coagulated is fully confirmed. Of 

 the ufual fluxes, only borax and microcofmic 

 fait have any effect on it. 



It is found in Golconda, Vifapour, Bengal, 

 the ifland of Borneo, and Brazil. 



The nature of cubic diamonds has notyet 

 been examined. 



Plumbago, Riifsbley, of the German's, Blyertz* 

 of the Swedes. 



This fubflance is externally black, but 

 bluifh white and fhining like a metal when 

 frefh cut : its texture is micaceous and fcaly, 

 yet granular. It is ufed for pencils. 



It 



