Silky filamentous Sulphate of Iron

Tab. 23 shows the beginning of this white silky substance by means of common moist air decomposing the pyrites, which is held in the black clay in such abundance in this specimen, as to separate and divide it so confusedly, that it is only recognizable by the little thin flakes, which still give out small floccose particles if a damp place. The green crystallized parts in this specimen are also forming into white wolly fibres. Whitby, in Yorkshire, has of old been favmous for alum works, as have other parts of the same county. My kind friend the Rev. James Dalton was so good as to send me specimens of alum ore from Mr. Baker’s Boulby works. it is a more compact ore than that from Glasgow. Dr. Travis, of Scarboro’, gave me some from Skowbrow, among which a baked specimen has some of the silky filaments remaining, as in Tab. 23. Alum has not been discovered native in England. it is said to be found abroad in octaëdral crystals, which is the form of the artificial ones. Of these I have a most superb specimen, sent by the Rev. James Dalton, from Mr. Baker’s alum works above mentioned; also some beautiful little crystals formed by agitation in a wine-glass, showing the lesser octaëdrons within the larger, and some curious modifications.

The crystallized specimen from Scotland has a prism.