CLASSIFICATION OF HIKEEALS. 107 



2. The characteristics of the second class, the metallic 

 minerals, are, 



Specific gravity exceeding 5*0. 

 Lustre metallic when scraped. 

 These are in the metallic state. 



Or specific gravity less than 5'0, but more than 2'5, and 

 they are destitute of the metallic lustre, but they are 

 Eeducible to the metallic state by the blowpipe, or 

 Rendered magnetic, or 



They volatilise wholly, or in part, producing a vapour, or 

 Communicate a colour to borax. 



Some of the substances of this class are combustible, but 

 their specific gravity greatly exceeds that of the combustible 

 minerals of class 1. 



3. The earthy minerals are characterised as follow : 



Insoluble in water. 



Tasteless. 



Incombustible at a white heat. 



Specific gravity less than 5'0. 



They are farther destitute of true metallic lustre when 

 scraped ; are not reducible to the metallic state ; nor do they 

 volatilise at a high temperature before the blowpipe. 



4. The saline minerals are 



Soluble in water, and 

 Impart a sapid taste. 



These classes are divided into orders, and some of the 

 orders into genera, and the genera again into families. 



The first class is divided into two orders, characterised by 

 their burning with a flame, or without it. 



The second class is also divided into two orders, the cha- 

 racteristics of which are volatilising, or not volatilising. The 

 first order is divided into genera, distinguished, the first, by 

 volatilising wholly ; the second, by leaving a residue reducible 

 to the metallic state with borax ; and the third, a residue not 

 so reducible. 



The characteristics of the families, into which the genera 

 of the first order are divided, are the absence or presence of 

 the metallic lustre. 



The characters of the genera of the second order are, the 

 being, or not being, reducible to the metallic state, either 

 with or without borax. The families are distinguished by 



