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
Pitinga mine By 1990 the mine directly employed 2,000 people, and indirectly perhaps as many as 40,000. Trees were cleared, the river diverted and dams and ponds built before the alluvium deposits were processed. Bucketwheel excavator dredges extracted material rich in cassiterite, which was pumped through pipes to floating processing plants that separated the tin ore. The cassiterite is concentrated on site, then shipped to Mamoré Mineração e Metalurgia in the southern state of São Paulo for casting. Columbite ore is also mined, concentrated and processed on site for use in production of FeNbTa metallic alloy. Up to 1990 a total of