Sulphuret of Molybdenum

This ore is said to have been found in Scotland. The specimens here figured arc, the upper one, from near Menabilly in Cornwall, and the lower one, from Coldbeck in Cumberland, and are now first published as discovered in these latter places. Mr. Sheffield first told me of its being found in Cornwall; and Mr. P. Rashleigh was so good as to procure me a specimen about a twelvemonth since; and about the same time I had some specimens of rocks from Kendal, among which was the one figured at the bottom of the plate. The first is lodged in small detached parcels very sparingly in largely plated Chlorite or Talc, among Arsenical Iron with some light Quartz; the latter in red Feldspar with Quartz and Mica, in which are interspersed smallish scattered particles of Pyrites, and the Molybdenum is dispersed in little particles, mostly on one broadish face, of a natural crack; but on the other sides of the stone, which is about half an inch thick, there is not the least particle to be seen. It therefore appears extremely local and partial. At first sight it has occasionally been confounded with Plumbago; but its micaceous foliated texture distinguishes it; besides, the lustre is truly metallic, and its colour bluer. Its folia are rather easily divided; it soils with less ease than Plumbago, and its mark is paler. It is bright in itself, and does not allow of being made brighter by scratching. I do not know that it has been found with determined crystals in Great Britain. As we possess many things besides the few that I have published, that have been chiefly ascribed to foreign habitats, I shall be glad to add them to our list^*.