9 



TAB. CCCV. 



CALX carbonata. 



Crystallized Carbonate of Lime, 



Class 2. Earths. Order 1. Homogeneous. 



Gen. Calx. Spec. Carbonata. 



Div. 1. Crystallized. Var. ilexaedral Prisms. 



Syn. Chaux carbonatee prismatique. Haiiy, 2. 141. 



J. he simple hexaedral column is among the scarcer forms 

 of this substance in Britain. 



The present specimens came from Cumberland. Crys- 

 tals of this form more rarely occur in Derbyshire. In 

 Scotland they are found at Strontian with Stilbite on the 

 opposite side of the specimen, as figured at tab. 258. In 

 some instances the whole form of the crystals is very neat, 

 and every face is polished. 



The upper specimen has not the end face polished, but 

 roughish. 



The lower specimen is most extraordinary, as on it the 

 crystals have very short columns and lie in various di- 

 rections, having both ends opaque, but are smooth and 

 polished on all the faces. The cause of polished faces 

 might seem to depend upon the gradual separation of the 

 menstruum or solvent from which it crystallized ; and a 

 great quantity might, by suddenly passing off, leave the 

 terminations of the crystals rough as in the upper specimens, 

 which are not finished at both ends ; the lower crystals 

 probably derive their opacity from a scanty supply of 

 water of crystallization at the ends. 



Some of the crystals in the upper specimen have the ter- 

 minal edges bevilled towards the column which leads to 

 other formations — see the next figure. 

 VOL. iv. c 



