Claistiial, Or Klansthal, a town of Prussia in the province of Hanover, situated on the Zel-lerbach, 26 m. N. E. of Gottingen; pop. in 1871, 0,138. It stands in a bleak district of the llartz mountains, on the top and slopes of a hill, about 1,800 ft. above the sea. It is regularly laid out, having been frequently burned down and rebuilt, but the houses are generally of wood. It contains a mining school supported by the government, with a good collection of models of mines and mining machinery and of minerals, a mint, a church, court house, and gymnasium. One of the mines reaches 500 ft. below the level of the Baltic, and is drained by a tunnel cut through the mountain to a distance of 6 m. The machinery of the mines is worked by water power, and every stream in the vicinity is carefully appropriated to this purpose; the various canals, which extend from mill to mill throughout the mines, have an aggregate length of 125 m. These mines have been worked since the 11th century. About 2 m. W. of Clausthal is the silver-smelting establishment, in which 13 stamping mills are used to prepare the ore for the furnace.