9-28 



IRON 



The Yorkshire ores occupying a somewhat uncertain position are placed -with the 

 argillaceous carbonates, p. 930. 



The iron ores of Lincolnshire which are placed by Mr. Jiidd in the greensand or 

 lower cretaceous formation (the neocomian of D'Orbigny) are thus described by him : 



'The existence in this district (the neighbourhood of Claxby) of fragments of 

 iron-slag, calcined ore, and charcoal, associated with Koman pottery, indicates that 

 these ores were known and worked at a very early period. 



' The only ironstone in this district (between Claxby and Nettleton) which is now 

 sufficiently rich to repay the working, is a rock almost entirely made up of small and 

 beautifully-polished oolitic grains of hydrated peroxide of iron. The earthy material, 

 full of large concretionary masses of ironstone, which was at first thought to be 

 equally valuable, is found to yield so small ah average 'percentage of iron, that it is 

 not worked. The oolitic ironstone rock is crowded with fossils, the shells of the 

 gigantic Pecten cinctus being especially abundant. It also frequently exhibits veins 

 of beautifully-crystallised calcspar. The ore is thus an eminently calcareous one : it 

 yields on analysis from 28 to 33 per cent, of metallic iron. 



' The useful bed of ironstone averages 6 feet 6 inches in thickness. It is mined by 

 means of adits driven into the face of the hill.' Quarterly Journal of the Geological 

 Society, 1870. 



In 1872, 62,653 tons were raised at Claxby; while at Froddingham, near Brigg, 

 256,149 tons were produced. 



Carbonate of iron ; Sparry iron ; Spathose iron ; Spathic iron ; Spharosidcrite ; 

 Spatheisenstein. This important species has been divided into two varieties ; spathose 

 iron proper, and the compact carbonate, the clay-ironstone of the coal-formation. 

 Sparry iron appears to range through nearly the same series of formations as the 

 anhydrous haematites : it occurs in beds and masses often of immense extent, especially 

 in Styria and Carinthia. In the Erzberg, near Eisenerz in Styria, it rests on gneiss, 

 and is wrought in an open quarry. The Stahlberg and Momel, near Schmalkald, the 

 vicinity of Siegen, and Miisen in Westphalia, show similar extensive masses ; whilst 

 in Anhalt and the Hartz it forms large veins in greywacke or in Devonian limestone. 

 Other very extensive deposits of this ore are found in the Pyrenees, and the Basque 

 provinces of Spain, as near Bilbao; and at Pacho near Bogota in New Granada. 

 Most of these localities yield fine crystals ; and these also occur in metallic veins at 

 Joachimsthal in Bohemia, Freiberg in Saxony, Clausthal in the Hartz, Beeralston in 

 Devonshire, Alston Moor in Cumberland, and in many of the mines of Cornwall, 

 where the rare hexagonal prisms have been found. In England the crystalline carbonate 

 of iron occurs in the Devonians of South Somersetshire and North Devon. It exists 

 in numerous lodes upon Exraoor, although they have been but partially worked. _ On 

 the Brendon and Eisen hills there have been mines for several years, those mines 

 producing in 1872, 27,913 tons. At Perranzabuloe in Cornwall an immense deposit of 

 spathose iron exists, and is now (1874) being worked to a considerable extent, a 

 railway having been constructed to carry the ore to the southern ports. It is also 

 found in the carboniferous limestones of Northumberland and Durham, especially in 

 Weardale, which district produced in 1872, 97,953 tons. 



The specific gravity of sparry carbonate of iron varies from 3'00 to 3*67- Its 

 primitive form is, like that of carbonate of lime, an obtuse rhombohedron. Without 

 changing this form, its crystals are susceptible of containing variable quantities of 

 carbonate of lime, till it passes wholly into this mineral. When heated before tho 

 blowpipe, it turns brown without melting, and becomes attractable by the magnet 

 after being slightly heated in the flame of a candle. Even by a short exposure to tho 

 air after its extraction from the mine, it also assumes the same brown tint, but with- 

 out acquiring the magnetic quality ; after long exposure to tho air it becomes wholly 

 converted into hydrated haematite. 



The variations in composition of this important mineral are shown in the following 

 analyses : 



