133 



TAB. CCCLXXI. 



S I L E X Idocrasis. 

 Idocrase, or Vesuvian Garnet. 



Class 2. Earths. Order 1. Homogeneous. 

 Gen. 4. Silex. Spec. Idocrasis. 



Syn. Hyacinthe var. 3 to 8. De Lisle, 2. 291. 

 Vesuvian. Emmerl. 3. 314. 

 Idocrase. Haiiy, 2. 5?4. 



It is found pretty abundantly in a rock chiefly composed 

 of Mica, Hornblend and Garnet, on Mount Sorama. The 

 present specimen was found in the county of Donegal in 

 Ireland, in what has commonly been called the Garnet 

 Rock, whieh is usually gathered in fragments for the sake 

 of the Garnet, for which this was sent to me j and is curi- 

 ous on account of its colour. The rock is composed of 

 Phosphate of Lime, large-grained primitive gray Lime- 

 stone, Quartz, in some parts coloured green by Phosphate 

 of Lime*, and Garnet, among which is the Idocrase or 

 Vesuvian of some authors, because it was first known as 

 coming from that neighbourhood. This substance is recog- 

 nised in the specimen, by its prismatic structure and rather 

 darker colour, although lighter than usual : the Garnet is 



* There are about the specimens several minute crystals of Phosphate of 

 Lime of a green colour, that bear some resemblance to Beryl. 



