132 DOMAIN IX. ANOMALOUS, 



STRUCTURE II. 



Garnet rock, interspersed with siderite, felspar, 

 and spangles of brown mica, from Portsoy in 

 Scotland. 



It seems essential to this rock that the garnet 

 matter should be dispersed throughout ; otherwise 

 gigantic and common garnets are sometimes so 

 closely mingled in mica slate, that the rock might 

 fall under this denomination. 



The garnet trap of Saussure, 258, of abrownish 

 green colour, composed of a mixture of particles 

 of steatite, fibrous hornblende, and mica, including 

 many little garnets of a dull red ? 



NOME XIII. SHORL ROCK. 



This rock is chiefly composed of the common 

 black shorl*, the black tourmaline of Haiiy, 

 which, according to Klaproth, contains 22 parts 

 of iron. It is common in granite, gneiss, and 

 other primitive rocks ; but is sometimes found to 

 form a rock by itself, or mixed with quartz. It 



* The word is original, and not derived from the town of Shorlau, 

 as appears from the term Shirl, used by the Cornish miners in the 

 same sense. 



