$i Element* of Mineralogy. 



fibrous texture, of a moderate hardnefs, not 

 fo great as to give fire with fteel ; fometimes 

 opake, fometimes pelliicid, fometimes regu- 

 larly chryftalized, and fometimes amorphous. 



Its fpecific gravity is 2,32 generally, fome- 

 times only 1,87. 



It is foliible in about five hundred times 

 its weight of water, at the temperature of 

 fixty. It does not effervefce with acids, and is 

 difficultly foluble in any, particularly in the 

 marine. 



When hedted a little below ignition, it un- 

 dergoes a motion fimilar to that of ebullition, 

 from the diffipation of its aqueous part* and 

 falls into powder ; if taken up when this 

 motion ceafes, and fprinkled over with water^ 

 it foon concretes and hardens, by reafon of 

 its fudden chryflalization. 



If calcined with J of its weight of char- 

 coal, it yields a liver of fulphur, and the 

 Earth thus feparated, treated with black flux, 

 frequently yields a little of Iron: it is fuiible 

 per fe by the blow pipe. 2 Bergman, 469, 

 or in a long continued porcelain heat, 22 

 Roz. 26, though Mr. Gerhard fays this does 

 not happen in crucibles of chalk, but only 

 in thofe of clay. 2 Gerh. Gefch. 16. 



It 



