392 Dr. F. H. Hatch — Iron-ores of the United Kingdom. 



Table showing average Analyses of Jurassic Ironstone as received* 



at the Works. 



Fe . 



Mn 

 Si0 2 

 A1 2 3 

 CaO 



MgO 



S . 

 P . 



Moisture 



Fe . 



Mn 



Si0 2 



AI2O3 



CaO 



MgO 



S . 



P . 



Moisture 



The Northampton Ironstone is, in general, high in silica and low 

 in lime, and contains 0*1 of sulphur and 0*6 of phosphorus. In 

 part, it is smelted locally with limestone or with limey ironstone, 

 obtained in the district, to neutralise its siliceous character. Some 

 is sent to Frodingham and some to Middlesbrough for smelting with 

 the ironstone of those districts, but the greater proportion goes to 

 furnaces in the coalfields of Staffordshire, Derby and Nottingham, 

 South Yorkshire, and South Wales, to be smelted in admixture with 

 the calcareous blackband and clay-ironstones of the Coal-measures and 

 with tap-cinder. 



The Cleveland Ironstone is also siliceous and requires lime to flux 

 it. It is high in alumina and sulphur, and this feature militates 

 against its use for making basic pig-iron, since the alumina-content 

 makes it difficult to carry sufficient lime in the slag to ensure the 

 production of a basic pig low in silicon and sulphur. To produce 

 a suitable pig a considerable proportion of ores low in alumina, mainly 

 of foreign origin, has to be added to the furnace charge. But, by 

 using molten metal direct from the blast-furnace and desiliconizing it 

 in a mixer, basic open-hearth steel can be made from Cleveland ores 

 without admixture with foreign ores. 



The Frodingham Ironstone almost invariably contains sufficient lime 

 to be fluxed without the addition of limestone. It also carries about 

 1 per cent of manganese and can therefore be smelted without the 

 addition of manganese ore. These self-fluxing properties make it 

 a most valuable ore, in spite of its low iron-content, which averages 

 onlv 22 per cent. The sulphur-content is 0"16 and the phosphorus 

 0-3*1. 



