Barytical Genus. 55 



times not harder than chalk, but moftly very 

 compact, and of a ftony hardnefs, though 

 never fo hard as to give fire with fteel. Its 

 texture lamellar or fibrous ; its fhape either 

 amorphous, orbicular, tabular, or criftated, 

 that is, jagged like a cock's comb, or chry- 

 ftalized in polygon prifms : it is alfo found 

 opake, femi-tranfparent, or tranfparent $ this 

 laft fort is an electric perfe. 



Its fpecific gravity is generally from 4 to 

 4,6, though ibmetimes, as Mr. Wiegleb re- 

 marks, it is not fo great. 1 1 Nev^ Endeck, 



It is infoluble, or nearly fb, in water, as 



well as in acids. 



The harder forts decrepitate in fire ; it does 

 not burn to Plafter of Paris as gypfum does ; 

 it is infufible />/"/ with a blow-pipe, yet Mr. 

 D'Arcet found the femi-tranfparent fort fufi- 

 ble in a long continued porcelain heat. 22 

 Roz. 26; probably becaufe it was placed in 

 an argillaceous veflel : but it is fufible by the 

 help of the mineral alkali, with effervefrence, 

 and alfo with borax and microcofmic fait, ac- 

 cording to Mr. Bergman. 



It is often mixed with calcareous Earth. 

 6 Roz. 222. 13 Roz. Supplement^ p. 408 

 4 



