1911 Encyclopædia Britannica/Idria

IDRIA, a mining town in Carniola, Austria, 25 m. W. of Laibach. Pop. (1900) 5772. It is situated in a narrow Alpine valley, on the river Idria, an affluent of the Isonzo, and owes its prosperity 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. As regards the quantity annually extracted, the mines of Idria rank second to those of Almaden in Spain, which are the richest in the world.