 Occurrence
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| In 2005, China was the top producer of cadmium with almost one-sixth world share closely followed by South Korea and Japan, reports the British Geological Survey.
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| Cadmium-containing ores are rare and when found they occur in small quantities. Greenockite (CdS), the only cadmium mineral
of importance, is nearly always associated with sphalerite (ZnS). Consequently, cadmium is produced mainly as a byproduct
from mining, smelting, and refining sulfide ores of zinc, and to a lesser degree, lead and copper. Small amounts of cadmium, about 10% of consumption, are produced from secondary sources, mainly from dust generated by recycling
iron and steel scrap. Production in the United States began in 1907 but it was not until after World War I that cadmium came into wide use.
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| A role of cadmium in biology has been recently discovered. A cadmium-dependent carbonic anhydrase has been found in marine
diatoms. Cadmium does the same job as zinc in other anhydrases, but the diatoms live in environments with very low zinc concentrations,
thus biology has taken cadmium rather than zinc, and made it work. The discovery was made using x-ray absorption fluoresence spectroscopy (XAFS), and cadmium was characterised
by noting the energy of the x-rays which were absorbed.
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