19 



TAB. CCCXIV. 



CALX carbonata, var. metastatica. 

 Metastatic crystallized Carbonate of Lime. 



Div. 1. Crystallized- 



This noble specimen of crystallized Carbonate of Lime is 

 curious, as a variety leading to a kind of Mackle that does 

 not seem to have been suspected ; but is not rare as to its 

 formation, for we often see ordinary specimens that partake 

 of it, having two of the opposite faces of each pyramid 

 much widened, forming a base to each parallel to the edge 

 of the primitive nucleus : this will be seen in the next 

 figure, which may be compared with tab. 33, the usual Meta- 

 static Mackle. The two facets, jig. 1, are primitive, a.nd fig. 2 

 are the same as those of tab. 34, lower figure , equiaxeds 

 but having those very obtuse- angled faces that so often 

 produce a rounding form, which help so much in the 

 numerous varieties of crystals in this substance, and are 

 extremely curious. Fig. 3 is a somewhat rounded edge 

 nearly on the angle of the pyramid. The facets, fig. 4, and 

 that opposite, are of the hexaedral column. Fig. 5, a facet 

 nearly on the edge of the nucleus. 



The rounded facets in Crystals are sometimes very de- 

 ceiving ; and the comparing this with the next plate will 

 prove the necessity of this leading specimen, which shows 

 the dividing angle of the natural face of the pyramids 

 parallel with the primitive edge, that divides the two pri- 



D 9T 



