216 DOMAIN II. SILICEOUS. 



STRUCTURE IV. COMPOSED OF TWO SUBSTANCES. 



Interesting examples of this kind occur at the 

 mines of Salzburg, and particularly at those of 

 Macugnaga, near Mount Rosa, in the north of 

 Italy. This rock has always been called gneiss, 

 but is composed of thickish plates of quartz, with 

 thin seams of foliated mica, or rather steatite. 

 Gneiss also occurs composed only of felspar and 

 mica. As the first of these kinds has been chiefly 

 observed in Italy, I would propose to call it 

 Pi 11 ** 6 ? from Pini, an illustrious geologist, who 

 explored the southern Alps. The other may be 

 called Ferberite, an honour due to Ferber, whose 

 travels illustrate many parts of Italy, and the 

 south of Germany. 



Aspect 1. Finite of quartz and steatite, from 

 Macugnaga, near Mount Rosa. 

 The same, from Salzburg. 



Aspect 2. Ferberite, from the Alps, &c. 

 Gneiss also occurs of quartz and siderite, and 

 of felspar and siderite. 



