REPORT OF THE DIRECTOR I917 193 



But whatever the explanation, the simple fact that both types of 

 ores under consideration, the Paleozoic Clinton ores and the modern 

 lake ores, generally contain both ferrous iron and soluble silica, 

 is strong evidence of a similarity of origin and, as the latter are 

 obviously direct chemical precipitates, there is this added evidence 

 that the same is true of the former. 



In both cases the details of the process of precipitation constitute 

 a difficult problem in colloid chemistry whose solution must be left 

 to the future. 



Sosman 1 has recently said, with reference to iron oxides in nature, 

 " Even the layman can get a vivid realization of the complexity 

 of the problems involved ; he has but to walk out through the country 

 round about Washington and notice the bewildering play of inorganic 

 colors everywhere about him, ranging from deep brown-black through 

 various shades of drab, brown, purple and maroon, and through 

 the many tints of pink, ochre and rose to the most brilliant reds 

 and orange-yellows, and then realize that almost every one of these 

 hundreds of colors is due to an oxide or hydrated oxide of iron; 

 he will begin to realize then that our chemical knowledge of these 

 oxides is almost infinitesimal." This passage, of course, refers to 

 geological conditions quite different from those under which the 

 iron ores were deposited, but the chemical problems involved are 

 essentially the same, and certainly are not simplified by the intro- 

 duction of the ferrous silicate factor. 



That the latter is something to be reckoned with in all attempts 

 to solve the problems, both geological and chemical, of the sedi- 

 mentary iron ores, seems to be a definitely established fact. 



In any given case, the relations of the silicate and the oxide must 

 be controlled by local conditions. For the Clinton ores, a pre- 

 dominant precipitation of hydroxide, with only subsidiary silicate, 

 is indicated. For the Wabana district, Hayes 2 reached the same 

 conclusion, while for European ores resembling the Clinton ores, 

 and notably the Minette ores of Lorraine, which are such a vital 

 factor in the present war, much difference of opinion exists. 



In most of these cases the amount of silicate, as compared with 

 oxide, is much greater than in the Clinton ores and the two grade 

 back and forth into each other repeatedly. That they have a most 

 intimate genetic relationship is evident and that one is derived from 

 the other by secondary processes is generally held, but there is no 



1 Op. cit., p. 72. 



2 Op. cit., p. 67-80. 



