482 



T. C. HOPKINS — CAMBRO-SILURIAN LIMONITE ORES 



bines with the iron, it is not sufficient to form the theoretical limonite. 

 Hence we must assume either that the water and iron combine in a 

 different ratio and form a new compound or. what is more probable, that 

 there is a mixture of the limonite and one of the other hydrous oxides. 

 1 have computed the hypothetical combinations of the elements given 

 in analysis number 1 on two bases, first assuming that the phosphorus 

 combines with the alumina to form wavellite, and, secondly, that it com- 

 bines with iron to form vivianite, and the silica combines with iron to 

 form griinerite. If one of the hydrous ferric silicates is formed, the pro- 

 portions would be changed slightly, as shown in a third combination. 

 After forming the wavellite, the remaining alumina is put in the form of 

 kaolin, and the remaining water and iron are combined so as to form all 

 the limonite possible, and the iron in excess is put into the goethite, 

 the next highest oxide. 



Per rent. 



Limonite, 2Fe 2 3 , 3H 2 77.79 



< loethite, Fe-A, H 2 8.07 



Griinerite, FeSi0 3 8.40 



Wavellite 78 



Kaolin 1.30 



2. 



Per cent. 



Limonite 75.65 



Goethite 9.61 



Griinerite S.59 



Vivianite. ... 1.95 



Kaolin 8.70 



The small per cent of manganese is supposed to be in the form of the 

 oxide. The lime and magnesia are presumably in the form of the 

 carbonate. 



Hypothetical Combinations of the Elements in the Limonite Ores 

 Computing the excess Silica as Anthosiderite 



Limonite 



Goethite 



Anthosiderite, 2Fe 2 3l 



9Si0 2 2H 2 



Wavellite 



Kaolin 



Quartz 



I<Y,,() : ;: B 2 (molecular] 



No. 5. 

 Bull bank. 



92.80 



5.91 



.;;9 

 .77 



49(5: 747 

 2 : 3 nearly 

 limonite. 



No. 1. 

 Hostler bank. 



478 



65.72 

 23.49 



4.05 

 .998 



1 . 29 



2.60 

 : 652 

 : 4 nearly. 



No. 2. 



Pennsylvania 



bank. 



No. 6. 

 Lytle bank. 



515 

 4 



54.23 

 39.95 



4.06 



.45 



.26 



.44 

 : 660 

 : 5 nearly. 



44. 

 44. 



506 : 6 

 4:5 



51 



70 



.39 



.76 



.61 



.44 



25 



nearly 



