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
Pnictogen be produced by fractional distillation of air. The principal method for producing phosphorus is to reduce phosphates with carbon in an electric arc furnace. Most arsenic is prepared by heating the mineral arsenopyrite in the presence of air. This forms AsO, from which arsenic can be extracted via carbon reduction. However, it is also possible to make metallic arsenic by heating arsenopyrite at 650 to 700 °C without oxygen. With sulfide ores, the method by which antimony is produced depends on the amount of antimony in the raw ore. If the ore contains 25% to 45% antimony by weight, then