Rutile is the next most abundant and contains around 98% titanium dioxide in the ore. It is mainly sourced from ilmenite, which is the most widespread titanium dioxide-bearing ore around the world. Both of which can be found at the Ries crater in Bavaria. Additionally two high-pressure forms are known minerals: a monoclinic baddeleyite-like form known as akaogiite, and the other has a slight monoclinic distortion of the orthorhombic α-PbO 2 structure and is known as riesite. Titanium dioxide occurs in nature as the minerals rutile and anatase. Star sapphires and rubies get their asterism from oriented inclusions of rutile needles. Leucoxene, fine-grained anatase formed by natural alteration of ilmenite, is yet another ore. rutile as a 'heavy mineral' in beach sand.

Rutile, and anatase, naturally occurring TiO 2, occur widely also, e.g. Synthetic TiO 2 is mainly produced from the mineral ilmenite. Together with rutile and brookite, one of the three major polymorphs of TiO 2. This is distinct from the crystalline forms in which Ti coordinates to 6 oxygen atoms. Molten titanium dioxide has a local structure in which each Ti is coordinated to, on average, about 5 oxygen atoms. The rutile structure is widespread for other metal dioxides and difluorides, e.g. The oxygen substructures are all slight distortions of close packing: in rutile, the oxide anions are arranged in distorted hexagonal close-packing, whereas they are close to cubic close-packing in anatase and to 'double hexagonal close-packing' for brookite. The overall crystal structure of rutile is tetragonal in symmetry whereas anatase and brookite are orthorhombic. The oxides in turn are bonded to three Ti centers. In all three of its main dioxides, titanium exhibits octahedral geometry, being bonded to six oxide anions.

6.2 Possible carcinogenicity by ingestion.

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