Calamine brass a mixture of the virtually indistinguishable zinc ores smithsonite and hemimorphite) as the zinc component of brass. The resulting brasses, produced by heating a mixture of copper and calamine to a high temperature for several hours (allowing zinc vapor to distill from the ores and permeate the metallic copper), contained a significant amount of slag material resulting from the non-zinc components of calamine. The use of ore rather than metallic zinc also made it difficult to accurately produce the desired final proportion of copper to zinc. This process is known as cementation. Calamine brass was produced using proportions of two-sevenths
Ore Mountains last silver mines closed and the company was disbanded. Mining in the Ore Mountains was given new life during the First and Second World Wars in order to supply raw materials. The Third Reich also saw the resumption of silver mining. Afterwards the people returned to the manufacture of wooden products and toys, especially in the Eastern Ore Mountains. The clock industry is centred on Glashütte. In the Western Ore Mountains, economic alternatives were offered by the engineering and textile industries. In 1789 the chemical element uranium was discovered in St. Joachimsthal; then in pitchblende from the same area, radium