388 E. C. HARDER AND R. T. CHAMBERLIN 



Some hard ore deposits, or parts of these deposits, are so massive 

 that the bedding is barely distinguishable while other portions may 

 be distinctly bedded. The material is generally well consolidated, 

 and some phases, especially the amorphous variety, are of extra- 

 ordinary hardness and toughness. 



Of the different varieties of hard ore the finely specular type 

 is the highest grade. It generally averages between 69 and 70 per 

 cent in metallic iron and rarely has more than o. 025 per cent phos- 

 phorus and frequently runs as low as 0.003 P^^ cent phosphorus. 

 Other impurities are practically absent. 



The soft, powdery ore deposits consist largely of unconsolidated 

 material of great fineness, most of it so fine-grained that it will 

 easily pass through a loo-mesh screen. Although fine, the material 

 is almost entirely crystalline, quite different from the amorphous 

 powder which occurs with much of the soft ore on the Mesabi 

 Range in Minnesota. Some of the powdery ore is slightly consoli- 

 dated when moist, but readily crumbles when dried. Most of it, 

 however, is soft in the moist state like fine moist sand. 



The powdery ore is dark blue in color like the hard ore and 

 resembles it in composition, though in general perhaps of slightly 

 lower grade as it is more frequently intermixed with a sprinkling of 

 quartz sand. It averages between 67 and 69.5 per cent metallic iron 

 and contains up to o . 05 per cent of phosphorus, though it may run 

 as low as 0.004 per cent of phosphorus. When the amount of 

 quartz sand increases in the soft ore the metallic iron content 

 decreases until the arbitrary figure of 50 per cent metallic iron is 

 reached, when the material is classified as itabirite. Some of the 

 soft ores, just as in the case of some of the hard ores, are almost with- 

 out evidence of bedding, while others are distinctly bedded and even 

 finely laminated. Where quartz sand is intermixed with the soft 

 ore the bedding is well marked. 



Hard ore and soft ore are generally more or less associated with 

 each other. In general it may be said that massive specular ore 

 and soft, powdery ore are hard and soft phases of the same material 

 (Fig. 13). A deposit composed principally of hard ore may 

 have lenses of soft ore or irregular masses of soft ore scattered 

 through it, or portions of it may be composed of a mixture of hard 



