Hydro-Oxyde of Iron
One of my former friends, the late Dr. Jackson, sent me this from Derbyshire in 1808, probably gathered at Nottingham, in the sandy remains that supply Fullers earth, see tab. 231 . I believe they are not rare there as I had formerly seen others very similar. Hydro-Oxyde of Iron causes many fanciful shapes; the present form is somewhat striking and may lead to information. Now to hazard a conjecture respecting their origin, they may possibly he formed by water containing Carbonate of Iron, making its way upward through the sand, depositing the Iron oxyde in its passage so as to give it permanency, I understand they are sometimes two or more feet long. I shall be glad of further information upon the subject, as I shall perhaps, have to say more about them hereafter. The sand attached to them has a few particles of Mica in it, and the grains are for the most part very small, but rather largest externally.
The cementing power of this Iron thus deposited is curiously exemplified in the other specimens from the Grit rock in Mortyn park quarry, by favour of Mr. Farey. The Clay has been separated from the surface of the Ironstone filling the remains of a reed, and the oxyde freed from its carbonic acid* has been left forming a crust on the outside, strong enough to make a complete oval neat box with nearly a flat bottom and top, including a nucleus of decomposing Ironstone shut up in it as if contrived by human art. It evidently belongs to the coal formation, as most Arundines are characteristic of it, and this has some small vestiges of coal on the outside.
- * Argillaceous Ironstone stains to be Carbonate of Iron mixed with Clay, the ochres and brown oxydes of Iron are in general found to contain water, and may, therefore, be distinguished chemically as well as mineralogically from the Red or peroxyde, which is free from water. The Systematical Index will show to which of these species each of the figures already given belongs.