Cobalt, a semi-metal of a whitish-grey colour, and nearly resembling fine hardened steel: it is as difficult to be fused as copper, or even gold ; and cannot be easily calcined. If the calx, resulting from that process, be melted with borax, pot-ash, or siliceous sand, it affords the blue glass, denominated by artists, smalt, which is principally employed in painting enamel, and in tinging other glass, being of all colours the most fixed in the fire. This semi-metal abounds in England, chiefly in the Mendip Hills in Somersetshire, and also in Cornwall, where it has lately been dug up in large quantities, and turned to considerable emolument.