IDRIA, a mining town in Austria, in the duchy of Carniola and circle of Loitsch, situated in a narrow Alpine valley on the river Idrizza, 28 miles north-northeast of Trieste. It is the seat of a circle court and of an office of mines, the building used for which is the old castle of Gewerkenegg or Gewerkenburg, built in 1527 by the miners during the lordship of the Venetian republic. The town also possesses a handsome church, a high school, a mining school, and a theatre. Linen weaving, lace making, and gin distilling employ a considerable number of the inhabitants, but the origin and prosperity of the town are due to the rich mines of quicksilver which were accidentally discovered in 1497. Since 1580 they have been under the management of the Government. The mercurial ore lies in a bed of clay slate, and is found both mingled with schist and in the form of cinnabar. A special excellence of the ore is the greatness of the yield of pure metal compared with the amount of the refuse. The mine is reached by a shaft 150 fathoms deep, and the descent is accomplished partly by means of ladders and partly by steps cut out of the solid rock. The number of miners employed is about five hundred; they wear a peculiar uniform. Formerly the mines were wrought by state prisoners, but notwithstanding the unhealthiness of the employment it is now largely sought after on account of the high wages offered to the workmen, as well as the pension allowed them when disabled, and the provision that is made for their widows and orphans. In 1870 improved ovens for smelting the ore were erected. The yearly yield of the mines is about 290 tons. The population of Idria in 1869 was 3813.