924 



IRON 



from Santander, and masses of the original mineral may be found unchanged in the 

 centre of some of the larger masses. 



When the original carbonate contains manganese, the derived brown ore will 

 generally bo associated with pyrolusite or other highly-oxidised manganese ores, 

 forming an intimate mixture suitable for simultaneous reduction, with the production 

 of a highly manganesiforous pig-iron. Such ores are common in the Siogeu districts 

 of Rhenish Prussia, and in the neighbourhood of Carthagena in Spain, from which 

 latter locality they are largely exported to England, Belgium, and other parts of 

 Europe. 



The largest developments of this class of ore in England are in the lower secondary 

 strata, where it is found at different horizons in- the oolitic rocks all through the 

 midland counties, from Wiltshire to Lincolnshire; the most important localities being 

 in Northamptonshire. As a rule these are of a low quality, containing not more than 

 35 per cent, of iron, with a considerable quantity of sand, and a high proportion of 

 phosphorus ; but from the low cost at which they can -be raised, being got in open 

 quarry workings, they are in great demand for mixing with the higher class but more 

 expensive ores of Wales and South Staffordshire, besides being largely smelted on the 

 spot. 



In addition to the ordinary atmospheric action, the production of brown iron ores is 

 largely due to organic agency in the so-called bog- and lake-ores, which are produced 

 by the action of minute vegetable organisms (diatoms), on iron in solution in stagnating 

 waters. These ores are generally very impure, containing large quantities of sand 

 and a good deal of phosphorus ; bog-ore is usually found in irregular concretions, 

 forming at times connected beds, but more generally they are detached in swampy and 

 forest-ground at a short distance below the surface. The lake-ores which are found 

 in Sweden and Finland are entirely of organic origin ; they form small granular 

 or disc-like concretions, which are dredged up from the beds of lakes during the winter. 

 The formation goes on continuously, so that, after clearing the ground, a fresh deposit 

 of workable thickness is re-formed in about twenty years. The varying nature of 

 ores of this class will be seen from the following analyses : 



Analyses of Brown Iron Ores from various sources. 



A special class of brown iron ores has of late become of considerable importance. 

 These are the aluminous ores, consisting essentially of mixtures of hydrated peroxide 

 of iron and alumina. The proportion of iron varies considerably, but they are valued 

 chiefly for the alumina, on account of its fluxing power, being used to prevent tin- 

 reduction of silica and the formation of extra siliciferous iron when smelting lia-in.Mtito 

 containing quartz. These ores are known as ' .Belfast aluminous ores.' from their oc- 

 currence in the county of Antrim ; and by the, mineralogica] name of llanxitr. from the, 

 locality in the south of France where it was first discovered. A yet more aluminous 

 variety is obtained in Carniola. The Irish ore occurs in a thin irregular bed of om- 



