a genus of fossils of the order of the aphoridata. In its purer states it is considerably compact and heavy, and not unfrequently of a semi-metallic appearance. Its texture is always fine; sometimes granulated, or composed of minute grains ranged into small strata; sometimes smooth and even, without any distinguishable grain. Its colour is sometimes a pale iron grey; sometimes a darker bluish or blackish grey. From variations of this kind, some mineralogists have divided it into distinct species, the principal of which are these. 1. Dark-grey cobalt; compact, ponderous, and of a very fine grain. This sort is said to be the most esteemed in Saxony, and to produce the finest blue glats. 2. Bright pale-grey, or ash-coloured cobalt, of a somewhat looser structure, and less ponderous. This kind has a great resemblance to the artificial pyrites, and some of the white silver and copper ores, from which those who are accustomed to the inspection of these minerals distinguish it pretty readily, by the colour of the cobalt being somewhat duller, and its texture finer. 3. Vitreous cobalt; in structure resembling melted scoria or glas, of a bright bluish-grey colour, called, by the Germans, Schlecken-kobold, flag cobalt. 4. Crystalloid cobalt, affecting chiefly a cubical figure sometimes perfect, but commonly with the angles imperfect. 5. Specular cobalt, intermixed with glittering talky flakes. 6. Earthy cobalt, blended with various earths into soft friable compounds, of a black, yellowish-grey, or other colours. 7. Flowers of cobalt. These are of a loose radiated structure, and generally not so heavy as the foregoing ores. The external parts are of a fine purplish red, a violet, or a peach-bloom colour. Sometimes the whole mass is elegantly tinged with these colours throughout; but more commonly the internal parts are of a greyish or leaden hue. They are never found in great quantities, or forming regular veins; but only in detached masses, lodged in crevices of stones; in places to which the air has had free access. They appear to proceed from a spontaneous revolution of some of the foregoing minerals; most of which are found to yield nearly similar effervescences on being exposed in heaps for a length of time to moist air. Wherever the workmen meet with these flowers, they expect a rich vein of cobalt in the neighbourhood.

Cobalt is found most plentifully in Saxony, particularly near Schneeberg in the district of Minna. The mines here are said to be two or three hundred fathoms deep; and the cobalt lodged at great depths to be of a better quality than such as is near the surface. The Schneeberg hill, according to the ancient chronicles of Saxony, yielded at first only an iron ore; which, on sinking deeper, about the beginning of the 14th century, was succeeded by a very rich ore of silver. This also being at length exhausted gave place to cobalt. Some pieces of the cobalt ores are still found to partake of silver, and even of gold; but these metals, far from being essential, as some have supposed, to all cobalts, are entirely accidental even in this. Cobalt has also been found in some parts of England, particularly in Mendip-hills in Somersetshire, and in Cornwall. Its quality, however, is found to be somewhat different from that found in Saxony. This country has long supplied all the world with zaffre and imalt, the most valuable productions from cobalt; great quantities of them being thence exported even to the East Indies. It is supposed that the Chinese, and more particularly the Japonese, had formerly mines of an excellent cobalt, from the produce of which were painted the fine blues of their ancient porcelains; but that these mines are now exhausted, and that the inferior blues of their present ware are painted with the Saxon zaffre imported to them by the Dutch.

Cobalt contains a great quantity of arsenic, and it is from this mineral that most of the arsenic we have is prepared. The greatest quantities are made at Geyerberg in Minna, from cobalt and other arseneical ores brought from Schneeberg. The ore is thrown into a furnace resembling a baking oven; whose flue is an horizontal pipe near 100 fathoms in length, considerably wide at the end which communicates with the furnace, and growing gradually narrower to the other end. The ore is every now and then stirred and turned in the furnace to promote the extrication of the arsenic, which arises in fumes into the pipe, and there condenses into a greyish or blackish powder called meal arsenic. This is refined by a second sublimation in close vessels, with the addition of a little potash which detains its impurities. In this operation, the fire which elevates the arsenic, heating the receiver, the flowers melt together into the crystalline masses brought to us. From cobalt, also, are prepared the substances called zaffre and smalt, used for tinging glats of a blue colour. See Zaffre and Smalt.

Regulus of Cobalt, a kind of semi-metal prepared from cobalt, of a whitish colour inclining to red. For the manner of its preparation, see Zaffre. For its chemical properties, see Chemistry, n° 159, 212, 213, 259.