IRON ORES 63 



tial that either the chemical, mineralogical, or phynic al fea- 

 tures of the various ores should be considered in detail. 



The early iron industry of the United States was based 

 largely upon bog ores, limonites, or other fonas of brown 

 hematites, obtained at points convenient to the Atlantic 

 seaboard. Magnetites also were employed at first by means 

 of a direct process whereby, in Catalan forges, the ores were 

 reduced and the resulting metal forged into l^looms or billets 

 without passing through the casting process; subsequently, 

 magnetites as well as hematites were smelted in blast furnaces. 

 But the later development of the iron industry and present 

 great importance are due largely to the use of red hematite 

 ore. 



The brown hematites and red hematites are of the same 

 chemical composition, in so far as iron oxide is the basis of 

 the ore, the primary differences being structural and the lower 

 percentages of combined and hygroscopic water in the red 

 hematites. Red hematites, if free from other impurities, 

 will yield 70 per cent of iron, and pure brown hematite, if 

 thoroughly dried out and calcined to eliminate all water, 

 will also yield the same proportion of iron. But if the ores 

 are merely dried to ch'ive off the moisture, which differs under 

 varying conditions, the amount of metallic u'on possible in a 

 pure red hematite is about 70 per cent, and in a pure brown 

 hematite 60 per cent. 



Magnetic ores are capable of yielding in the pure state 

 more metal than any other ores, and ptire magnetite would 

 show 72.48 per cent of metallic iron, but magnetites, like 

 the hematites, are subject to deterioration from other ele- 

 ments which are present. 



The fourth form of iron ore is the carbonate or spathic, 

 in which the oxide of iron is associated wdth carbonic acid 

 and generally with lime. If this carbonic acid is driven off 

 by heat carbonate ores become practically brown hematites, 

 but in the natural state the purest carbonate would not jdeld 

 over 46.7 per cent of iron. Considerable of the early iron 

 industry, particularly in western Pennsylvania, eastern and 

 southern Ohio, Kentucky, and Marjdand, and also to a cer- 

 tain extent in eastern New York, was based upon the use 



