Hydro-Oxide of Iron

Having some time had a desire to exhibit some varieties of Ironstone, I now feel a satisfaction in adding the present specimen to British Mineralogy. It occurs in a stratum of indurated Marle that rests on a thin seam of Surturbrand, (see tab. 189) called, in such a situation, Coal: the Surturbrand is mixed with striated Gypsum, which beneath is crystallized in abundance in a looser Marle, immediately above the Sandstone that is over the Subsulphate of Alumine; see tab. 499. The impression of the leaf looks like the larger foliage of the Platanus orientalis; but as the impression does not expose the extremities, it cannot be yet determined^*, In the same mass are the remains and casts of bivalves^†, perhaps Cyclades, resembling the Linnean Mactra solida or subtruncata, which is also found abundantly in company with the Cerithia in the bed of Blue Clay above, at Woolwich. Thus we have some indication of a contemporary formation: the shells at Woolwich are abundant, and much in the same state of preservation. A cast of an Unio also accompanies the Cyclades in this ferruginous stone. I do not know how it is in Wiltshire, where the Ironstone so much resembles Scoria, and is peculiar for its strange impressions, which I can only compare to the cast of some shell that has a low spire, but the inside seems to have a subdivision that gives it the appearance of being double, and the termination when perfect is like the end of a ram’s horn. I hope, from the inquiries now making, to see these more perfect for Mineral Conchology. These casts are accompanied by many other species, but not so distinct as I could wish; the mass often includes little Flints, whole or broken, or bits of Chalk; but is often full of hollows like Iron Scoria: it is certainly only a deposition of Oxide of Iron bom water, cementing together any thing in its way, as rusty iron often does. I have added a specimen at the bottom of the plate.