Sapphire (Heb. sappir; Ar. safir), a precious stone, next in value and hardness to the diamond. It is a transparent variety of corundum, composed of nearly pure alumina. It receives different names according to the color, the red sapphire being the oriental ruby; the amethystine, the oriental amethyst; the yellow, the oriental topaz; the green, the oriental emerald; while the term sapphire alone is commonly applied to the blue variety. The Greek sapphire ( ) was not the gem here described, but the lapis lazuli, as appears from the description given by Theophrastus and Pliny. The blue sapphire is the of the Greeks and the hyacinthus of Pliny. The ruby was probably included in the anthrax of Theophrastus and the carbunculus and lychnis of Pliny. The chemical formula of sapphire is A14O3, with a small quantity of oxide of chromium, upon the varying proportions of which the color of the different varieties depends. The coarser kinds of corundum contain several other oxides. (See Corundum, and Emery.) The sapphire crystallizes in the rhombohedral system, has a vitreous lustre, often pearly in the basal planes, and sometimes, when viewed in the direction of the vertical axis, exhibits a bright opalescent star. All sapphires, or pure varieties of corundum, are exceedingly tough and hard, being rated 9 on the scale of hardness, the diamond being 10. The gem is found in various parts of the world, and in different geological formations, as in the granite of Siberia, in the ripidolise of North Carolina, and in the granular limestone of New Jersey. The finest ruby sapphires come from Pegu, Burmah, and Siam. Smaller ones have been found at Hohenstein in Saxony, Bilin in Bohemia, and Le Puy in Prance. The finest blue sapphires come from Ceylon. - The blue sapphire has been known from the earliest times, and was regarded by the ancients as a sacred stone.
It is the fifth stone in the breastplate of the Hebrew high priest. A good blue sapphire of 10 carats is worth about 50 guineas, and one of 20 carats 200 guineas. An ordinary rule for estimating the value is to multiply the square of the weight in carats by half a guinea. Fine gems, for special reasons, often bring a much higher price; thus a sapphire of a barbel blue, weighing 6 carats only, brought at a public sale in Paris $350. Notwithstanding its excessive hardness, the ancients executed fine engravings upon the sapphire. A remarkable intaglio by Cneius, cut in a sapphire, is in the Strozzi cabinet at Rome; it is a profile of the young Hercules. - The red sapphire, or ruby, is the most precious variety, a perfect one weighing more than 3 1/2 carats being more valuable than a diamond of the same weight; a perfect one of 5 carats is worth twice as much as a diamond of the same weight; and when they weigh 10 carats each, the ruby, if very fine, has three times the value of the diamond. According to Harry Emanuel ("Diamonds and Precious Stones," London, 1873), the finest and purest rubies have the following value: 1 carat, from £14 to £20; 2 carats, £70 to £80; 3 carats, £200 to £250; 4 carats, £400 to £450. The tint of the ruby is as fine by artificial light as by the light of day, and when of the finest tint it has the color of the centre of the red band of the solar spectrum, or that particular shade known by jewellers as "pigeon's blood;" but it varies from the lightest rose tint to the deepest carmine.
A deep-colored ruby exceeding 20 carats is usually called a carbuncle. The largest fine ruby known in the world was brought from China to Prince Gagarin, governor of Siberia; it afterward came into the possession of Prince Menshikoff, and is now in the imperial crown of Russia. The mines of Burmah are a royal monopoly, and the finest stones can be carried out of the country only by smuggling. When a particularly large and fine stone is found, it is customary to send out a procession of grandees with soldiers and elephants to meet it. One of the titles of the king is "lord of the rubies." The yellow sapphire, called the oriental topaz, is very rare, but never reaches the value of a ruby or blue sapphire, or even an emerald of equal dimensions. It was the second stone in the breastplate of Aaron. It was for a long time supposed that the ancients did not engrave upon the topaz, but Caire describes one in his possession weighing 29 carats, engraved with the motto in Arabic, "No one accomplishes but God." The ordinary occidental topaz is a compound of alumina, silica, and fluoric acid. (See Topaz.) The violet sapphire is the oriental amethyst, a very rare gem of a magnificent lustre.
It is the ninth stone in the breastplate of the Hebrew high priest, and is the sacred stone which ornaments the cross and the pastoral ring of Catholic bishops. It was often cut both in relief and in intaglio by the ancients. In the national library of France there is a splendidly wrought profile in amethyst, supposed to be Maecenas in old age, engraved by Dioscorides, one of the four celebrated engravers mentioned by Pliny. The greater part of the amethysts of commerce are occidental amethysts, quartz crystals colored a fine violet by certain metallic oxides. (See Amethyst.) The oriental emerald, the green variety of precious corundum, when of a beautiful green and perfectly transparent, is the rarest of gems. Specimens have been found in Montana territory. (See Emerald.) When the sapphire is colorless it is called the white sapphire, and when properly cut and polished it has been mistaken for the diamond; but it is inferior in brilliancy, and may be distinguished by its somewhat less specific gravity, and by its being readily scratched by the diamond. - Specimens of sapphire have been found in the ripi-dolite of North Carolina by Col. C. W. Jenks, in large crystals of several hundred pounds weight.
They occur in the native rock in situ, of different colors, possessing much beauty as mineralogical specimens, and some of them have been cut; but as they are traversed by cleavage planes, they do not possess the perfection of the eastern gems. - Artificial sapphires have been formed by Deville and Caron in small crystals by subjecting fluoride of aluminum to the action of boracic acid at a white heat, and adding various quantities of fluoride of chromium. A certain quantity yields the blue sapphire, somewhat more the ruby, and still more the emerald. Daubrée formed pure crystals by the action of chloride of aluminum on lime; Ebelmann by exposing to a high heat four parts of borax and one of alumina; and Gaudin by decomposing potash alum with charcoal.