Question: whats chromium

David Pyle answered on 19 Mar 2011:

It’s an important transition metal, which is fairly abundant in the Earth – and probably very abundant in the Earth’s metallic core. Chromium is an important oxidant, and forms many toxic compounds.

Chromium compounds are often strongly coloured (and that’s the origin of the element’s name). The gem and jewellery industry would be a lot poorer without Cr – ruby is only red because of the trace amounts of Cr present in the structure (pure Al2O3 is colourless); and emerald is only green because of the trace amounts of Cr present.