Group 12 element zinc and cadmium which makes geological separation unlikely. As a consequence, cadmium is produced mainly as a byproduct from mining, smelting, and refining sulfidic ores of zinc, and, to a lesser degree, lead and copper. One place where metallic cadmium can be found is the Vilyuy River basin in Siberia. Although mercury is an extremely rare element in the Earth's crust, because it does not blend geochemically with those elements that constitute the majority of the crustal mass, mercury ores can be highly concentrated considering the element's abundance in ordinary rock. The richest mercury ores contain up to 2.5% mercury
Schlangenberg Nature Reserve the interest in the ore which was mostly used for weapons and vessels. The greatest interest in calamine had been in the 18th century when brass manufactures settled in Stolberg (Rhineland). For the production of the alloy they needed large amounts of calamine which was melted together with copper. Before 1800 digging small reaching only surface based ore was the only technique available to the miners. In the 19th century mining changed and more than 20 adits enabled the workers to reach calamine up to 105 m below the surface. During this time the Schlangenberg-area was perforated like a Swiss