64 JOHN BIRKINBINE 



of carbonate ores, but because of the facts that these ores 

 in their natural state are lean, that they usually occur in 

 veins that must be worked underground, often deteriorating 

 as workings are extended, and that the ore must be roasted, 

 the quantity of carbonate iron ores employed has been greatly 

 reduced. 



In late years the quantity of magnetic iron ores utilized 

 annually in producing pig iron has increased but slightly, 

 although some remarkable deposits of these ores are avail- 

 able. But magnetites are not as readily reduced as the hema- 

 tites, are often dense and hard, are liable to have an excess 

 of sulphur, phosphorus, or titanium, or are so closely asso- 

 ciated with the gangue matter as to make them lean, de- 

 manding that roasting or some method of concentration, 

 either by hydraulic or magnetic separators, should be em- 

 ployed. 



Brown hematites occur mostl}^ in pockets or lenses, but 

 are occasionally found in strata, often associated closel}^ 

 with limestone, and also more or less intimately mixed with 

 clays and siliceous matter. Consequently, many brown 

 hematites require washing to separate the clay and sand, 

 and in some cases this washed ore is subsequently roasted 

 to drive off the excess of moisture. 



All methods of beneficiating ores, such as roasting, wash- 

 ing, and separating, add to the expense of production, and 

 it is therefore not surprising that red hematites, which seldom 

 require preliminary treatment, have met with general favor. 



The distribution of iron ore throughout the United States 

 is general; there is no state in which iron ores of some kind 

 are not found in considerable quantities, but all are not avail- 

 able for use. 



In some cases the ores are too lean, that is, carry too 

 small a percentage of iron; in others deleterious elements, 

 such as phosphorus, sulphur, silica, and titanium, are in ex- 

 cess. Some deposits are too far from desirable fuel, or too 

 inconvenient to blast furnaces, to make their immediate 

 utilization practicable; others are in small bodies or veins, 

 or are scattered over too large areas to make their exploita- 

 tion profitable. It is probable that some of the undeveloped 



