Chap. 12.] 



CHAP. XII. 



PONDEROUS EARTHS. 



Jtarytes ajcarce Mineral ; found in t<wo States. ~ Crijlatum, Pon- 

 derous Spar. Caiv&.-~-Li f ver Stone. 



BARYTES is found in two ftates, combined either 

 with the carbonic or vitriolic acids, ift. When 

 united with the former acid, it refembles alum, but 

 is hard and ftriated, as if compofed of radiating fibres 

 coming from a center. This mineral has only been 

 found native in a lead mine at Anglezark in Lanca- 

 fhire. It is fometimes of a greenifh colour j fome- 

 times jagged, when it is called criftatum y from its re- 

 femblance to a cock's comb. Thefe prorhiHences are 

 found accreted to balls of the fame fubftance. Later 

 inveftigations have however clafled this as a fulphat of 

 Barytes. 



2. Ponderous earth is more frequently united with 

 vitriolic acid, and in this date it is found in all the 

 Derbyfhire and Cumberland lead mines, and in feveral 

 coal pits throughout England. Thefe ftones are 

 found of various appearances, pale yellow, blackifh, 

 with coarfe fcales, or with fine fparkling fcales. They 

 are either tranfparent or opake. The tranfparent 

 PONDEROUS SPAR is ufually in the form of a fix-fided 

 very flat prifm, ending in a four-fided pyramid j but, 

 like all other cryftals, liable to be varied by the cir- 

 cumftances attending their formation. The opake 

 fpecimens, called CAWK. by the miners, are of a white, 

 grey, or fawn-colour j frequently of no regular figure, 

 but often in the peculiar figure of a number of fmall 



F 3 convex 



