THE MINERALOGY OF SCOTLAND. 



359 



IDOCRASE. 



From Delnabo, Glen Gairn, Aberdeenshire. Idocrase occurs abundantly, passing 

 when massive almost insensibly into garnet in the old limestone quarry. The portion 

 taken for the analysis was a portion of a magnificent dark brown crystal of about 

 7i inches in length by nearly 1 inch in width, which was fractured by the blow which 

 disclosed it. Its specific gravity was 3 '43. 



On T302 grammes — 



Silica, . 











. -45 



from Alumina, -022 



•472 = 36-251 



Alumina, . ... . . 18-626 



Peroxide of Iron, 













•932 



Ferrous Oxide, 













5-036 



Manganous Oxide, 













•844 



Lime, 













33-935 



Magnesia, 













1-574 



Potash, . 













•568 



Soda, 













•329 



Water, . 













1-78 



99-875 



Insoluble silica, L483 per cent. 



