Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/484

 ciently 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 larger concretionary masses of ironstone, which was at first thought to be equally valuable, is found to yield so small an average percentage of iron that it is not worked. The oolitic ironstone rock is crowded with fossils, the shells of the gigantic Pecten ductus being especially abundant ; it also frequently exhibits veins of beautifully crystallized calcspar. The ore is thus an eminently calcareous one ; it yields on analysis from 28 to 33 per cent. of metallic iron ; in many places it appears to have undergone a certain amount of dehydratation, and exhibits irregular patches of dull reddish tints. The great value of this ore consists in its adaptability for smelting in admixture with the argillaceous ores of the coal-measures ; and the whole of the rock at present raised is sent to Leeds for that purpose.

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 : the working of this ironstone, however, is rendered less profitable, owing to the want of a good roof to the seam, and the consequent necessity for heavy timbering. The adits at the present time (December 1869) have extended for some 200 yards into the hill, and at the furthest point an upcast shaft, about 90 feet deep, has been put down. The ore is carried on a private railway, about mile long, to the Holton-le-Moor station on the Manchester, Sheffield, and Lincolnshire Railway. For a considerable time past the ironstone has been raised and sent away at the rate of about 100 tons per day.

The ironstone beds are known to extend as far northwards as Hundon, where they are of considerable thickness ; and a thin seam of the same rock has been found as far southward as Tealby.

The similarity in every respect of this ore with that which has been worked for many years at Steinlahde and Osterholz, near Salzgitter, and at some other points in Northern Germany is very striking. The German beds, which are among the various strata of somewhat different ages classed together by M. Fr. Ad. Romer as Hilsconglomerat, are, like the English strata, more or less completely made up of minute, polished, spherical, oolitic grains of hydrated peroxide of iron. The English and the German ironstones are, both as rock-specimens and in polished sections under the microscope, quite undistinguishable in their characters. The fossils also in the two cases are almost identical, and the extraordinary abundance and great size of the specimens of Pecten ductus are in both alike remarkable. "While, however, the English beds are almost horizontal, the German strata are greatly inclined (at Steinlahde at an angle of 63°), and can therefore be worked by means of great open pits. Similar oolitic ironstones to those of Lincolnshire and North Germany occur in the Neocomian of France and Switzerland*.

Greensand of the Isle of Wight (Quart. Journ. Geol. Soc. vol. iii. pp. 302, 308) are very different from those we have been describing, consisting of grains of
 * The oolitic iron-ores mentioned by Dr. Fitton as occurring in the Lower