CLASSIFICATION OF ORE DEPOSITS. 



-Geologist, November, 1889, p. 291, to a precipitation from oceanic 

 waters in the vicinity of submarine volcanic eruptions from whose 

 ejectamenta they derived their iron and silica. The hypothesis is 

 regarded as sufficient to account as well for the siliceous deposits 

 associated with the ore. In the words of the authors : " Chemical 

 precipitation in hot oceanic waters, united with simultaneous sedi- 

 mentary distribution, might produce the Keewatin ores in a man- 

 ner consistent not only with the physical conditions that prevailed 

 at the time of their formation, and with the structural peculiari- 

 ties which they exhibit, but also in accordance with the known 

 reactions of heated alkaline waters, and with the chemical char- 

 acter which the ores are known to possess." This hypothesis in- 

 troduces new conditions and relations which are necessarily some- 

 what speculative ; and while it has claims to attention, it may 

 best be tested by the general consideration of the geological pub- 

 lic before being placed with the more simple and certain reactions 

 grouped in the scheme. 



1.06.25. Fahlbands should be mentioned here. The term re- 

 fers to belts of schists, which are impregnated with sulphides, but 

 not in sufficient amount in the locality where the name was first 

 applied (Kongsberg, Norway) to be available for ores. The de- 

 composition of the sulphides gave the schists a rusty or rotten ap- 

 pearance that suggested the name. Whether the ores are an 

 introduction into the schist, subsequent to metamorphism, or a 

 deposit in arid with the original sediment, is a doubtful point. The 

 practical importance of these fahlbands lies in the enriching in- 

 fluence that they exert on the small fissure veins that cross them. 



1.06.26. The phraseology of the above schemes will be employed 

 in the subsequent descriptions. In addition, much emphasis will be 

 placed on the character of the rocks containing the deposits, 

 whether unaltered sedimentary, igneous, or metamorphic, and 

 whether in the first and last cases igneous rocks are near, for these 

 considerations enter most largely into questions of origin. The 

 ore deposits are illustrated by examples, somewhat as has been 

 done by the best of modern writers abroad, Von Groddeck. The 

 word "example " is preferred to "type," which was employed by 

 Von Groddeck, because it implies less of an individual character. 

 "We may cite deposits under different metals thus which all might 

 belong to one type. Under each metal will be given, first, a list 

 of general treatises and papers. These will be marked "Hist." 

 when especially valuable as history, and " Rec." when recom- 



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