MURPHREE'S VALLEY; MANGANESE ORES. Ill 



with a knife; soils the fingers; streak black, unmetallic, fine 

 texture, granular or massive, brittle, cleavage not perfect, 

 breaks in any direction. 



A somewhat similar ore, but combining 10 per cent, of 

 water, is called Manganite. It differs mainly from the 

 Black Oxide in being harder, having perfect cleavage and 

 being generally fibrous or columnar in structure. 



2. PSILOMELANE. This ore has not a definite chemical 

 composition, but usually carries from 60 to 70 per cent, of 

 dioxide of Manganese. This ore is harder than the preced- 

 ing, and varies more in color, running from light brown to 

 black. It is often associated with pyrolusite, in the same 

 bed, or even in alternate layers. It can generally be dis- 

 tinguished by its greater hardnes, and its streak being 

 more reddish, or brownish, and shining, or sub-metallic. 



Another variety resulting from one or all of the preced- 

 ing ores is called Wad. It is generally soft or pulverent, 

 often light, impure, much mixed with foreign matter. It 

 has resulted in all cases from the decomposition of the other 

 ores. And is not therefore of any definite chemical compo- 

 sition. Color always brown to black, soils fingers freely. 



All these ores are known in the markets by the rather in- 

 definite and uncertain name of "per-oxide of Manganese" 

 That is an ore containing the largest amount of Oxide. But 

 the market demands that they shall contain at least 60 per 

 cent of it. Any ore which does not contain as much as 60 

 per cent of dioxide of Manganese is not saleable. 



The 3rd common form is MANGANIFEROUS IRON ORE. It is 

 so called because the oxide of iron predominates in it, over 

 the oxide of Manganese. The respective oxides may vary 

 between wide limits in different specimens ; but when the 

 dioxide of Manganese runs as low as 20, or even 30 per cent., 

 and the oxide of iron predominates, it is called "Manganif- 

 erous iron ore" Its usual color is brown, blue black, or 

 black; and in hardness and density it approximates limonite. 

 A good deal of ore often called pyrolusite* properly belongs 

 to this class. 



