Minium, or Red Oxide of Lead

This new and truly curious production is unusually interesting, as being found naturally formed, and will probably afford a lesson for the chemist, as the work of the great Laboratory of Nature: especially as it exposes a subject usually formed by a sort of volcanic process, if I may so term it, and which yet has here every appearance of a Neptunian origin. Possibly the very process of thus procuring it may be of consequence enough to teach us how to preserve its most inimitable tint, which has hitherto been a great desideratum. It should seem by the nature of the specimen that something has wrought a sort of furrow or concave passage through the Galæna, and that this was a very powerful menstruum, penetrating it so deeply in some parts, and in such a manner, as to give the appearance of worm-holes; these holes are lined with the Oxide of Lead of the usual scarlet colour, in a fine-grained powder, about the thickness of paper, adhering to the Galæna rather closely, and which, when separated, shows a dull roughish site with a corroded appearance. Upon the surface of the Minium we may almost recognise a substance between Massicot and Litharge, about the same thickness, separating in irregular patches, in extremely fine particles, which, with a magnifying glass, seem to sparkle, and have something of a scaly appearance. In some parts they are of a lighter yellow and nearly white, as the colouring of the figure indicates.

In a letter to Sir Joseph Banks, from Smithson Tennant, Esq., it will he found that he has lately discovered this substance abroad^*.

Gathered by W. E. Sheffield, Esq. in a lead mine near Craven in Yorkshire.