185 



TAB. CXCVIII. 



CALX carbonata, var. ferrifera. 

 Ferriferous Carbonate of Lime. 



1 his is part of a superb specimen collected last summer 

 by John George Children, Esq. at Audlim mine, about 

 eight miles from Bodmin, Cornwall, and is somewhat the 

 more remarkable as it used to be said that Carbonate of 

 Lime was not to be found in Cornwall. The whiter pari of 

 the specimen is a cavity handsomely filled with crystallized 

 Carbonate of Lime of a very uncommon modification, 

 being nearly an hexaedral plate with the equiaxe and pri- 

 mitive bevellings, if I may so call them. It is rather re- 

 markable that the external surfaces of these crystals are 

 whitish, and the inside of a rich dark brown, as the darker 

 surrounding part shows*. Tab. 62. British Mineralogy 

 is nearly of the same nature, but under common circum- 

 stances grows blacker by exposure to the air. 



This specimen has many other curious circumstances of 

 change and position of mineral substances attending it; 

 viz. the redder parts are a sort of Camelian Quartz, some- 

 what approaching Chalcedony, coloured by a rich Oxide of 

 Iron, and this is sometimes covered by Cachalon : see 

 British Mineralogy, tab. 111. 



* This specimen has probably been broken from an opposite piece, and 

 was given to the worthy Mr. Rashleigh. 



