Titanium dioxide is a naturally occurring oxide of the element titanium. Also referred to as titanium (IV) oxide or titania, this substance also occurs naturally as three mineral compounds known as anatase, brookite, and rutile. However, it is most commonly extracted from titanium tetrachloride by carbon reduction and re-oxidization. Alternatively, it may be processed from another oxide called ilmenite, which is subjected to reduction with sulfuric acid to achieve pure titanium dioxide.