a genus of precious stones, of a blue colour, and the hardest of all except the ruby and diamond. They are found in the same countries with the ruby; also in Bohemia, Alsace, Siberia, and Auvergne. Mr. Rome de l'Isle mentions one found at Auvergne, which appeared quite green or blue according to the position in which it was viewed. Cronstedt, however, informs us, that the blue fluor spar is frequently met with in collections under the name of sapphires; and it is certain from Pliny, B. 37, chap. 9, that the sapphire of the ancients was our lapis lazuli. They are seldom found of a deep blue colour throughout, or free from parallel veins; and when they are but slightly tinged, they are named white sapphires. The late unfortunate king of France had one with a stripe of fine yellow topaz in the middle. Some are found half green and half red, and are foliated like the ruby. The fine hard sapphires, called by the jewellers oriental, are of the same nature with the ruby and topaz, excepting the mere circumstance of colour. They are commonly in two oblong hexagon pyramids, joined at their base, and pointed at top; sometimes also in hexagonal columns.

The finest sapphires, like most of the gems, come from the East Indies. Russia does not produce the sapphire. In Scotland they are found of a hardness and lustre equal to the oriental, both light and deep coloured, at Benachie, and Invercauld, Aberdeenshire; Portsoy in Banffshire, and many other places. Mr. Deuchar, seal-engraver in Edinburgh, has in his possession a beautiful sapphire, which was found in a double crystal. On one of these is cut a head, which was effected with the greatest difficulty, on account of its hardness; the other is cut into facets, and has a fine water, and great brilliancy.

The specific gravity of these precious stones, according to Bergman, is from 3.650 to 3.940. According to others the specific gravity of the oriental sapphires is 3.994; that of the Brazilian 3.1307; and of those from Puy in Auvergne, 4.0769. When powdered, they are fusible with borax, or microcosmic salt, into a transparent glass; and the same thing happens on treating them with magnesia alba. They are said to lose their colour by fire, and to become so hard and transparent as sometimes to pass for diamonds; but Mr. Achard found this to be a mistake, and that the true sapphires are not in the least altered either in colour, hardness, or weight, by the most intense fire. Those of Puy in Auvergne, however, though by their colour and hardness they seem to approach the oriental sapphires, lose both their colour and transparency in the fire, becoming black, and even vitrifying, which plainly shows them to be of a different kind. Engelbreth informs us, that the sapphires, in their rough or native state, generally crystallize in two oblong hexagonal pyramids pointed at top, and joined at their bases, but are sometimes found of an hexagonal or columnar form.—A good sapphire of ten carats is valued at 50 guineas; if it weighs 20 carats, it is valued at 200 guineas; and, if under ten carats, its value may be found by multiplying the carat at 108.6d. by the square of its weight.—Sapphires are preferable to common rubies for jewelling watches, on account of the homogeneous hardness of their substance; some red stones resembling rubies being met with, which are not uniformly hard.