KLAUSTHAL, or Clausthal, in the circle of Zellerfeld and the district of Hildesheim, Prussia, is the chief town and mining centre of the Upper Harz. It is situated on a bleak plateau, 1860 feet above sea-level, and unites to form one town with Zellerfeld on the opposite bank of the Zellbach. The streets are broad, opportunity for improvement having been given by fires in 1844 and 1854; the houses are mostly of wood. Klausthal has a famous mining college, with a mineralogical museum, and a minesurveying and a mining school. There is also a disused mint. The men of the town are mainly employed in the neighbouring mines and smelting works; of the latter the most important is the Frankenscharner silver smelting house, where American as well as German ore is worked. The population in 1875 was 8539; including Zellertød, it was 12,799.

Klausthal was founded about the middle of the 16th century, after the erection of the Benedictine monastery at Celia. Mining was carried on by the monks, and more energetically by the dukes of Brunswick, who brought miners from Franconia.