JD. H. Browne — Phosphorus in Iron Mtn., Mich. 307 



difference between these ores and the soft blue hematites oc- 

 curring east of the Menominee River. The ore taken from 

 the l^anainio, Paint River, Iron River, and other non-Bessemer 

 mines has all the non-laminated, massive, porous, reddish-yellow 

 appearance of an altered bog ore. With this also the frequent 

 occurrence of graphite, the high phosphorus, the intermixed 

 calcareous matter, and the low percentage of iron seem to 

 agree. From such beds as these, I incline to think the iron of 

 our soft blue hematite mines has been carried. It is interesting 

 to notice how this supposition is strengthened by chemical 

 proofs. I have often noticed that very dilute solutions of hot 

 acids will dissolve from an ore almost all of its phosphorus, with 

 only a slight percentage of iron. Indeed it is possible, in this 

 way, to remove and estimate the phosphorus without bringing 

 the ore into solution. Nor is acid always necessary, for in a 

 large number of instances also verified by experiment I have 

 found that ore exposed for several years to the weather will 

 have appreciable amounts of phosphorus dissolved and removed. 

 Now if water acidulated by carbonic acid acts on a bed of bog 

 ore, it will carry therefrom a large amount of phosphorus in 

 proportion to the amount of iron removed. If such thermal 

 water flows into a shallow valley or lake, the acid will be lost 

 by evaporation, and precipitation of phosphorus and iron will 

 take place. 



The theory of aqueous deposit of these ore bodies, as drawn 

 from chemical evidence, is then briefly as follows. From pre- 

 viously deposited beds of bog iron ore, by the action of acidu- 

 lated water, iron, lime, silica and phosphorus were dissolved. 

 The first solution contained a large amount of phosphorus in 

 proportion to the amount of iron dissolved. On coming into 

 hollows in the surface of the exposed slates, the acid solution, 

 losing acid by evaporation, deposited iron, as hydrated oxide, 

 which carried down an amount of phosphorus proportionate to 

 the amount of iron precipitated. As the acid became still, 

 weaker crystals of carbonate of lime and magnesia settled out, 

 forming a layer of carbonates. A second inflow of water 

 would tend to dissolve these carbonates and precipitate another 

 layer of iron. In similar manner by successive inundations the 

 depression became filled with alternating layers of iron ore 

 and calcium-magnesium carbonates, each layer being as a rule 

 lower in phosphorus than the preceding one. As the carbon- 

 ates were more soluble than iron, the probability is that the 

 greater portion was replaced by iron ore. Moreover as both 

 calcium and iron phosphate are of lower specific gravity, and 

 more soluble than the hydrated oxide of iron, the tendency of 

 the water was to carry these phosphates toward the lower 



Am. Jour. Sci— Third Series, Vol. XXXYII, No. 220.— April, 1889. 

 20 



