Idocrase (Gr. to resemble, and a mixture), a mineral species of the garnet section of the silicates, resembling other species in its crystalline forms. It occurs variously colored, as brown, sulphur yellow, green, and blue; and of vitreous, frequently somewhat resinous lustre. Its hardness is 6.5; specific gravity, 3.35-3.45. It was first observed in the lavas of Vesuvius, and was called Vesu-vian. Numerous localities of it are known in gneiss rocks, serpentine, and granular limestone. It is particularly abundant at Parsons-field and Phippsburg, Me., occurring in massive forms as well as in crystals.
Idria (a mining town of Austria, in the duchy of Carniola, 28 m. N. N. E. of Trieste; pop. in 1869, 3,960. The town is in a deep, narrow Alpine valley, on a small river of the same name. Its quicksilver mines are the second in importance in Europe, and in 1871 produced 6,700 cwt, besides about 1,100 cwt. of artificial cinnabar. The rich hepatic mercurial ore is found in a formation of clay slate forming a bed in compact limestone. The excavations are horizontal galleries diverging from a shaft which has been sunk to a depth of more than 1,000 ft. The entrance is from the Schloss, a building within the town. Descent is accomplished partly by about 800 steps cut in the rock, and partly by ladders. The miners are a uniformed corps, 500 in number, and the service is eagerly sought for, the higher rate of wages and contingent advantages being balanced against the unhealthiness of the occupation. The mines were discovered in 1497, and are the property of the crown.
Iglau (a town of Austria, in Moravia, on the Iglawa, 46 m. W. N. W. of Brunn; pop. in 1869, 20,112. It consists of the town proper, which is walled, and three suburbs, and contains a military school, a gymnasium, and several charitable institutions. It has manufactories of woollen goods, tobacco, glass, and paper, and spinning and dyeing works. On July 5, 1436, the convention was concluded here, by which the emperor Sigismund was acknowledged king of Bohemia.
Iglesias (a town of Sardinia, in the province and 32 m. W. N. W. of the city of Cagliari; pop. about 6,500. It derives its name from its great number of churches. So many gardens adjoin it that the Sardinians call it fiore di mundu (flower of the world). The finest of these gardens is at the Dominican convent. The richest lead mine of the island is on Monte Pone, 1,100 ft. high, 1 m. S. W. of the town.
Ignacio Yriarte, a Spanish painter, born in the province of Guipuzeoa in 1620, died in Seville in 1685. He was the most celebrated of Spanish landscape painters, but did not excel in figures, which in several of his works were painted by Murillo.