a genus of precious stones of various colours; as, 1. Of a deep red colour inclining a little to purple; the carbuncle of Pliny. 2. The spinell, of the colour of a bright corn poppy flower. 3. The balas or pale red inclining to violet; supposed to be the mother of rubies. 4. The rubicell, of a reddish yellow. According to Cronstedt, the ruby crystallizes into an octoedra form, as well as the diamond, from which it differs very little in hardness and weight, whence he concludes that they are both of the same nature; but some late experiments have shown that the diamond differs excessively from all other gems, in being displicable by a strong fire, which the others resist. Tavernier and Dutens inform us, that in the East Indies all coloured gems are named rubies, without regard to what their colours may be; and that the particular colour is added to the name of each in order to distinguish them from one another. There are, however, some soft stones of this kind which they call lazans; and it is certain, that the hard and brilliant rubies named oriental, as well as the sapphires and topazes, are all the same, excepting only the circumstance of colour. Some are partly red and partly blue, yellow, and some quite colourless. The spinell rubies are about half the value of diamonds of the same weight; the balas is valued at 30 shillings per carat. Tavernier mentions 108 rubies in the throne of the great Mogul, from 100 to 200 carats, and of a round one almost 2½ ounces: there is also mention made by other travellers of rubies exceeding 200 carats in weight. According to Dutens, a perfect ruby, if it weighs more than 3½ carats, is of greater value than a diamond of the same weight. If it weighs one carat, it is worth 10 guineas; if two carats, 40 guineas; three carats, 150 guineas; if fix carats, upwards of 1000 guineas.

According to the experiments of Bergman and Acharde, the texture of the ruby is foliated like that of diamonds; it is fusible with borax in a strong and long continued heat, running into a transparent glass of a pale green colour: the same effect is produced by microcosmic salt; but with sedative salt, or mineral or vegetable alkali, the glass is opaque and differently coloured. From the experiments of M. d'Arrect, it appears that the ruby does not lose its colour in the greatest fire; but Henckel says, that, by means of a burning glass, he softened it in such a manner as to receive the impression of a seal of jasper. It becomes electric by being rubbed. Its specific gravity, according to Bergman, is from 3.180 to 4.240; but Briffon tells us that it is 4.283. The specific gravity of the spinell is 3.760, of the Brazilian-ruby 3.531.

Rubies are met with in the Caepa mountains of Pegu in the East Indies; and at Caos, Ava, Bifnagar, Calicut, Cananor, Ceylon, and Brazil. They are found in the sands of rivers of a red colour, in an argillaceous earth of an hard texture and greenish colour: sometimes they adhere to red rocks. The spinell rubies are met with in Hungary, Silecia, Bohemia, and Brazil. The balas comes principally from Brazil, though some are also brought from the East Indies. The rubicell comes also from Brazil, but are said to lose their colour in the fire. A variety of this gem, but of a soft quality, is found in great plenty on the sea-shore near Ely in Fifeshire, Scotland. There is also a stone, which comes near to the ruby found near Portfoy, Banffshire, and at Inverary, Argyleshire, Scotland. The rubino di rocca of the Italians is a true garnet of a deep red and violet, or of the amethyst colour. What is called ruby of arsenic or of sulphur is the realgar: the ruby of zinc is the red blend; and the ruby of silver is the red silver ore.

Rubies may be artificially made from Brazilian topazes of a smoky appearance, by giving them a gradual heat in a crucible filled with ashes, until it be red-hot.

Rock Ruby, the amethystonitas of the ancients, is found in Syria, Calcutta, Cananor, Cambaya, and Ethiopia. It is the most valued of all the species of garnets, and is frequently sold as a ruby under the name of rubinus Rufficum. See Garnet and Ruby.