Chromium is an odourless, hard, steel-grey coloured metal that takes a high polish. The principal ore from which chromium is extracted is chromate. Chromium has three main forms - metallic chromium (0), chromium (III) and chromium (VI). Chromium (III) occurs naturally in the environment and is an essential dietary nutrient. Metallic chromium (0) and chromium (VI) are produced by industrial processes.