254 ECONOMIC GEOLOGY 



each 0.02 per cent, in excess of 0.2 per cent, of phosphorus. The 

 Brazilian ore carries only 0.03 per cent, of phosphorus. The ore 

 dried at 212 at Chicago allows 12 per cent, of iron and remain- 

 ing moisture. The Brazilian ore carries but 7.6 per cent, of iron 

 and water combined. The tenor of manganese required is 40 

 per cent., while the ore carries 54.8 per cent, manganese. The 

 ore, therefore, is destined to make Brazil one of the principal 

 competitors in the world's markets, and to supply quite largely 

 the manganese ores for the United States. The Michigan and 

 Wisconsin ores carry 8 per cent, of manganese. The residues 

 of Franklin Furnace, New Jersey, carry from 14 to 25 per cent, 

 of manganese. The Vermont ores carry from 30 to 50 per cent, 

 of manganese. The Arkansas ores contain from 40 to 50 per 

 cent, manganese. Therefore none of the American ores are so 

 rich in their manganese content as the Brazilian deposits of the 

 metal. These lower grade ores are best adapted for the manu- 

 facture of brick, glass and^chemicals. 



India and Russia also possess enormous deposits of manganese 

 ore. 



Geological Horizon. The ores of manganese are not confined 

 to any particular geological horizon. (See Fig. 127.) They 

 appear in the Appalachian belt in the Cambro-Silurian formations. 

 In Arkansas the formations bearing manganese range from the 

 Ordovician to the Carboniferous. In the Harz Mountains the 

 ores are Lower Permian. In California some of the deposits are 

 as late as the Jura-Trias. In fact, bog manganese is in the process 

 of formation to-day in the same manner and through the same 

 agencies as bog iron ores. 



Methods of Extraction. Metallic manganese may be manu- 

 factured by the action of metallic sodium upon the chlorides of 

 the metal, or by the Goldschmidt process. In this process the 

 ores of manganese are converted into their oxides by roasting. 

 The oxides are treated with aluminum at a high temperature 

 when the oxide of aluminum, A1 2 O 3 , is formed and the manga- 

 nese is reduced to the elemental state. The process depends 

 upon the fact that aluminum has a greater affinity for oxygen 

 than manganese. 



Uses of Manganese. Before the advent of the Christian era, 

 manganese was used to color porcelain violet, purple, brown and 

 black. A small amount of manganese imparts a violet color, 

 and an excess of manganese produces a jet black. This black 



