*TOME XII. GARNET 



necessity of introducing the ferruginous or side- 

 rous among the other earths. 



This curious rock seems unknown in any sys* 

 tern of mineralogy, except Mr. Kirwan's, who 

 says, " Garnet-rock of Karsten, found by him 

 near Winneburg : it consists of amorphous gar* 

 net, in which trap, quartz, calcareous spar, and 

 a very small quantity of blackish brown mica are 

 found."* 



But the garnet rock, recently discovered in 

 Scotland, seems to consist of that matter minute- 

 ly interspersed among siderite and felspar, with 

 larger or smaller globules, or imperfect crystals 

 of garnet. In some parts it seems to approach 

 to slaty siderite, penetrated with garnet ; as it is 

 common for that schistus to contain garnets. , 



The surface is brown from the decomposition 

 of iron ; and the garnets are of a coarse texture, 

 and irregular form. 



STRUCTURE I. 



Amorphous garnet rock, containing trap, quartz, 

 calcareous spar, and mica, from Winneburg. 



* Min. i. 368. The Scotish may be the rock with grains of garnet 

 from Sweden, Norway, &c. Linn, a Grarelin, 223. The Saoeum 

 MoJare Grariaticum, colore rulente, of Wallerius, from Norberke in 

 Sweden. 



