280 KEMP'S ORE DEPOSITS. 



etc., Amer. Jour. Sci., September, 1891, p. 231 (the paper is con- 

 cluded in the American Geologist, December, 1891), brings out 

 the fact that alkaline carbonates, of which calcium carbonate is one, 

 precipitate from solutions of ferrous sulphate or ferrous carbonate, 

 under ordinary conditions, hydrous ferrous carbonate, an unstable 

 salt that quickly oxidizes to a hydrous oxide. The argument is then 

 adduced that bodies of siderite or anhydrous ferrous carbonate 

 could not have originated by direct precipitation, but have prob- 

 ably done so by pseudomorphous replacement of calcium carbonate. 

 The author then follows the possible metamorphism or changes of 

 these bodies to other forms of iron ore, citing, however, some as 

 possible examples that are clearly unwarranted. The chemical 

 distinctions thus brought out undoubtedly have their weight and 

 importance ; but siderite as a frequent veinstone crystallizes as the 

 anhydrous carbonate, and in surroundings giving no reason to in- 

 fer that it has replaced calcium carbonate. It has also been ob- 

 tained artificially by several investigators (as cited by Fouque and 

 Levy in Synthese des Mineraux et des Roches), and there is still 

 reason for believing that it does not necessarily always form in 

 nature as a pseudomorph after calcium carbonate. 



Page 74. Attention has been lately directed to the great de- 

 posits of bog ore in the Three Rivers district of Quebec. (P. H. 

 Griffin, " The Manufacture of Charcoal-Iron from the Bog and Lake 

 Ores of Three Rivers District, Province of Quebec, Canada," Trans. 

 Inst. Min. Eng., Montreal meeting, February, 1893.) Although the 

 deposits have been long known and have been the basis of a small 

 industry, they are now utilized on a larger scale for car-wheel iron. 

 They occur in the small lakes and swamps that receive the drain- 

 age of the old Laurentian highlands on the north. This water, 

 more or less charged with iron, drops its burden as bog ore wher- 

 ever it stands. By collecting supplies from a fairly extended dis- 

 trict, quite large amounts of ore are obtained. The deposits fur- 

 nish ideal illustrations of the general origin of bog ores, as outlined 

 in preceding pages. They occur also on the bottoms of lakes and 

 are obtained by dredging. The lake ore seems to run somewhat 

 richer than that gathered in the bogs. Both are low in sulphur 

 but have about 0.3$ phosphorus. 



Page 78. Volume I. of the Annual Report of the Geological 

 Survey of Arkansas consists of a report by R. A. F. Penrose on 

 the " Iron Deposits of Arkansas." It at once appears that there is 

 little prospect of Arkansas producing any notable amounts of iron 



