In 1556, Agricola already referred to the existence of the mineral lupi spuma (the name means wolf's foam), today known as wolframite. It was so called due to the apparent tin "eating" during the extraction, like the wolf eats the sheep. The German name "wolfram" and symbol W are probably associated to this primordial denomination. In 1781, Scheele showed that the mineral known nowadays as scheelite, was a salt of calcium from a new acid, tungstic acid. In the same year, T. Bergmann recognized that the tungstenic acid was an oxide of a new element, which as called tungsten, from the Swedish expression to heavy stone. Metallic tungsten was produced for the first time in 1783 by J. J. and Elhuyar Don Fausto, two Spanish chemists that performed the reduction of the oxide with carbon.