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TAB. CCCLXXX. 



BARYTES sulphata. 

 Sulphate of Barytes. 



Div. 1. Crystallized. 



This figure leads from nearly the primitive thickish rhom- 

 boidal prism to the flatter plated crystals, which are piled 

 by the side of each other upon one of their most acute edges, 

 [see tab. 70,) consequently giving it a very different appear- 

 ance from the right-angled plates more usually seen, as in 

 tab. 72, the edges of which are parallel to the diagonals. 

 The crystals upon this specimen are mostly truncated upon 

 the acute solid angles, the truncations forming little trian- 

 gular facets; and they are all so deeply truncated at the 

 obtuse solid angles, that the truncations meet. Tab. 70, 

 bottom figure^, shows one of these faces ; and Tab. 95 ex- 

 hibits both. 



This specimen came from Dufton. It is convenient here, 

 as it partly leads to those flatted primitive forms that stand 

 on the acute edges and are often very thin, without any de- 

 crement on the angles, but occasionally passing by minute 

 degrees towards an elliptical form, produced as it were by 

 being placed by the side of each other when forming, but 

 slipping or falling a little out of the parallel with those above 

 or below. This sometimes seems the cause of the curved- 

 like appearance which happens in Sulphate of Barytes like 

 that of Pearl-spar, tab. 19 ; more particularly when the latter 

 is a flatter variety. The weight and pearly lustre will, how- 

 ever, most generally distinguish them. The next figure 

 partakes of this appearance. 



