68 Elements of Mineralogy. 



In fire it becomes more brittle and whiter, 

 but is infufible perfe by the blow-pipe, and 

 fcarcely fufible by fixed alkalis, but more 

 completely, and with little effervefcence, by 

 borax or microcofmic fait. 



This talc contains fomething lefs than 50 

 per cent, of filex, and about 2 percent, of iron. 

 The magnefia is in fmalier quantity, but it 

 exceeds the argill : the exaft proportion I 

 have not found. 



Mufcovy talc confifts of broad, elaftic, 

 flexible, tranfparent leaves, and differs exter- 

 nally from mica only in being fofter and more 

 foapy to the touch. 



SPECIES VII. 

 Combined with the Sparry Acid. 



This combination is fcarcely foluble in wa- 

 ter, but has not yet been difcovered ia 

 nature. 



SPECIES VIII. 

 Combined 'with the Tungften Acid. 



This compound when artificial is alfo info- 

 luble, but has not as yet been obferved native. 



Compound 



