134 



irregular, somewhat more salmon-coloured, and lighter; the 

 Phosphate of Lime nearly white, and the gray at the bot- 

 tom is the coarse-grained Limestone of the county, which 

 is generally considered as primitive. The whole rock is cer- 

 tainly a curiosity, if considered in a geological point of view. 



The small upper specimen has the Idocrase of the more 

 usual darker and shining greenish brown, and the Garnet 

 is crystallized j which assists in identifying it. 



The crystal of the Idocrase is a rectangular four-sided 

 prism, with the lateral planes streaked and the edges most 

 commonly truncated. It is without its termination in my 

 specimen; but Haiiy exhibits a great variety of faces upon 

 the short or obtuse pyramidal apex. It has a resino-vitreous 

 appearance with very little transparency. It is hard enough 

 to scratch glass. Its specific gravity is from 3*0882 to 

 3*409. Melts with borax into a yellowish glass which ap- 

 pears red while hot. 



Analysis of Idocrase, from Mount Somma. 



Alumine 



Silica 



Lime 



Oxide of Iron 



Oxide of Manganese 



Loss 



Thus we add another substance to British Mineralogy. 

 The specimens were sent, some time since, by Dr. Scott 

 of Dublin, without determining it. I say no more on this 

 substance at present, hoping some time or other to see 

 more perfect crystals, with less confused fracture and ter- 

 minations, and also of the Beryl-like Phosphate of Lime. 



16-25 , 



. 22-25 



42-00 . 



. 35-50 



34-00 



. . 33-00 



5-50 



. . 7'50 



se 



. . 0-25 



2-25 



. . 1-50 



