tAB. XCVI. 



Div. 2. Imitative. 



1 mfc variety of sulphate of barytes has obtained the name 

 of cauk among the miners; for what reason I do not know. 

 It has also been called terra ponderosa. The sort here 

 .figured is very frequent in Ecton mine, Staffordshire, It 

 is not uncommon in other places, but of a less regular spbse- 

 rical form, It is generally accompanied by carbonate of 

 lime, fluor, galaena, blend, iron and copper pyrites, &c, 

 and is most frequently white. Sometimes it is coloured by 

 oxide of iron, and is then either yellowish, or mostly 1 

 reddish. The specimen represented in the upper figure 

 came from Ecton mine, and is accompanied by calcareous 

 spar and pyrites of various forms and hues. The internal 

 structure is confusedly laminated, showing signs of crystalli- 

 zation, arranged in the form of a sphere; these laminae 

 are extremely close, and often confused, or so thin that 

 «io determinate form can be made out, having only the 

 appearance of segments of circular plates, sticking edgewaj 

 by the side of each other: see the bottom figure: at otheF 

 times they are the edges of plates with the faces usual to 

 tabular sulphate of barytes ; see tab, 72. The whole are. 



