USEFUL METALS is. 



Magnetite, Fej0 4 , 72.4 per cent. Fe. The only iron-black 



mineral strongly .magnetic before heating. 



Franklt'nit,; (Fe,Mn,Zn)O,(Fe,Mn) 2 O,, 44.1 per cent. Fe. 

 ( >cciirring in black octahedrons which vary in the degree of mag- 

 netism and in the per cent, of iron with the amount of manganese 

 and zinc present. 



Hetmititf, I'YjOs, 70 per cent. Fe. The only mineral with cherry 

 red or blood red streak. It includes the specular iron ore, the 

 Clinton ore, and the fossil ore. 



Gdthite, Fe 2 O 3 ,H 2 O, 62.9 per cent. Fe. 



Xanthosiderite, Fe 2 O 3 ,2H 2 O, 57.1 per cent. Fe. 



Turgite, 2Fe 2 O 3 ,H 2 O, 66.2 per cent. Fe. 



Limonite, 2Fe 2 3 , 3H 2 O, 59.8 per cent. Fe. 



Of the last species named only one of them appears crystallized 

 and that is gothite. They are all classified in the trade as limon i t < 

 and their fine powders vary in color from reddish-brown to yellow. 

 The last named mineral, limonite, occurs in compact forms, 

 sometimes in a pulverulent state, sometimes in stalactitic forms, 

 in bog ores, and as brown clay-iron stone. 



There are also many arsenides, arsenates, chromates, tungs- 

 tates, columbates, niobates, etc., of iron but these are not of 

 sufficient importance as a source of iron to be considered here. 

 In fact, the minerals of which iron is an essential constituent are 

 numbered by the hundreds. 



The iron minerals of economic significance fall distinctly into 

 four classes: 



(1) Those used for the extraction of the metal. These in the 

 order of their importance in America are, hematite, limonite, 

 magnetite, and siderite. The production of each in 1905 was 

 hematite 86.6; limonite 8.8; magnetite 4.5, and siderite 0.12 per 

 cent, of the total. In England siderite is said to furnish more 

 than 50 per cent, of the pig iron of Great Britain. 



(2) Those used in their natural state as pigments after reduc- 

 tion to impalpable powders; hematite, limonite, and to a limited 



' extent franklinite. 



(3) Those used for the extraction of an acid radicle. For tin- 

 extraction of sulphur are: pyrite, marcasite, and pyrrhotite. 

 For arsenic of commerce: lollingite, FeAs 2 , leucopyrite, FesAs4, 

 and arsenopyrite, FeAsS. For the extraction of chromic acid: 

 chromite, FeO,Cr 2 3 . For the extraction of tungstic acid: 

 wolframite, (Fe,Mn)W0 4 . For the extraction of titanic acid: 



