Genth.] 94 [Feb. 6, 



sufficient state of purity to throw light upon their constitution, as they 

 were crystalline, and free from visible impurities. For this reason they 

 wei'e examined separately. 



Taking into consideration only their principal constituents, viz : Ferric 

 oxide, Silicic acid and water, the question arises, in which form the 

 silicic acid is present, as it is undoubtedly in chemical combination with 

 the ferric oxide and not in the form of a mechanical admixture of sand. 

 If pieces of these fibrous limonites are placed into strong chlorhydric 

 acid, all the ferric oxide will be extracted, and the silicic acid will remain 

 in the shape of the original pieces, of a snow-white color and fibrous 

 structure. The only hydrous ferric silicates, which are known, are An- 

 thosiderite and Degeroeite. The former is a crystalized mineral, which 

 has a composition, represented by the formula 2Fe203, OSiOj+BHjO. 

 It is very probable that, although observed in its pure state only at one 

 locality, it occurs frequently as an admixture with other iron ores. — If 

 we calculate for the 3.98 per cent, of silicic acid in the fibrous mineral 

 from Bull Mine, the requisite quantities of ferric oxide and water, we 

 find 3. 36 per cent . of ferric oxide and 0. 26 per cent, of water, making an 

 admixture of 6.60 per pent, of anthosiderite. The atomic ratio between 

 the remaining 79.12 per cent, of ferric oxide and 13.64 per cent, of water 

 is 1 : 1.53 or very near 2 : 3, showing the hydrous ferric oxide to belimo- 

 nite = 2 Fe, 0.„ 3 Hj O. 



If in the same manner we examine into the composition of the fibrous 

 mineral from the Dry Hollow, the 2.47 silicic acid require 1.46 per cent, 

 ferric oxide and 0.17 water, giving an admixture of 4. 10 per cent, of 

 anthosiderite. — The atomic ratio between the remaining 81 .67 per cent of 

 ferric oxide and 12.75 per cent, of water is 1: 1.4, which also shows the 

 ferric hydrate to be limonite, which, however, has already lost a small 

 part of its water. 



The above analyses show besides the mechanically admixed rounded 

 grains of sand, which I distinguish as "quartz," a considerable quantity 

 of silicic acid, which is in chemical combination, probably as a hydrous 

 ferric oxide. But as it is impossible to say what the true character of 

 this mineral may be, whether anthosiderite, or degeroeite a silicate of 

 the composition Fe.^ O.^, 2Si02+3H20 or a species not yet known in its 

 pure state, suffice it to say that all these ores are mechanical mixtures 

 of limonite with hydrous ferric silicate and minute quantities of hydrous 

 ferric phosphate, perhaps dufrenite or cacoxenite ; some of the ores con- 

 tain besides these, small quantities of manganese ores, mostly the so- 

 called "bog-manganese" or wad, but also pyrolusite and psilomelane. 



It is a very remarkable fact that, although these iron ores are to a great 

 extent at least, the result of the decomposition of limestones and by them 

 precipitated, that almost the entire amount of lime has been washed 

 out of them and only traces are remaining ; of the second constituent of 

 the limestones, the magnesia, a somewhat larger quantity is left be- 

 hind, owing undoubtedly to the lesser solubility of its carbonate in car- 

 bonic acid water. 



