IDRIA, a mining town in the province of Gorizia, Italy, 29 m. N.E. by road from Gorizia. Pop. (1931) 5,698 (town), 10,629 (commune). It is in the narrow Alpine valley of the Idria, an affluent of the Isonzo, and has rich mines of quicksilver acci dentally discovered in 149o. The mercurial ore lies in a bed of clay slate, and is found both mingled with schist and in the form of cinnabar. The yield of pure metal is high compared with the amount of the refuse. The mines of Idria rank second to those of Almaden in Spain, which are the richest in the world.