in chemistry, a mineral often confounded with plumbago or black lead, but possessed of different properties. It is composed of scaly laminae of various magnitudes, scarcely adhering to each other; somewhat greasy to the touch, foiling the fingers, and leaving traces on paper of a blackish grey colour. In powder it is of a bluish colour.

"Perfect molybdena (says Mr Fourcroy) slightly detonates with nitre; the residue contains molybdene, tartar, and calx of iron. From the experiments of Mr Scheele, molybdene appears to consist of a peculiar combustible matter and iron. The nature of the combustible matter is not yet perfectly known. Mr Hielm, a disciple of the celebrated Bergman, appears to have succeeded in converting it into a regulus. Mr Pelletier affirms, that he has had the same success; but the properties of this new metal have not yet been examined. The molybdenic acid appears to be a metallic one. Its weight, its flinty and astringent taste, its dry and pulverulent form, its fusibility, insolubility, the colour it assumes by action of flame and combustible matters, its precipitation by nut-galls and the acid of Prussian blue, show that it is somewhat similar to the arsenical acid. This substance is so rare in France, that no chemist except M. Pelletier has had an opportunity of making a regular series of experiments upon it. It is greatly to be wished that they should be continued, especially with a view of deciding whether the molybdenic acid be truly different from all others; for I cannot avoid thinking, notwithstanding its peculiar characters, that a substance which does not become acid but by the assistance of 30 parts of weak nitrous acid, and is with so much difficulty brought to assume the saline state, ought not to be considered as an acid truly peculiar."

See Chemistry-Index; and Mineralogy, p. 134.

Molybdene is found sometimes along with tin-ores and iron-ores, that are attracted by the magnet, among copperiferous pyrites; and also with wolfram, in Saxony, Iceland, Sweden, France, Spain, &c.