rutile

{{Infobox mineral | name = Rutile | category = Oxide minerals | boxwidth = | boxbgcolor =#5e5048 | boxtextcolor = #fff | image = Rutile-ww7a.jpg | imagesize = 260px | caption = | formula = TiO2 | IMAsymbol = Rt | molweight = | strunz = 4.DB.05 | system = Tetragonal | class = Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) | symmetry = P42/mnm | unit cell = a = 4.5937 Å, c = 2.9587 Å; Z = 2 | color = Brown, reddish brown, blood red, red, brownish yellow, pale yellow, yellow, pale blue, violet, rarely grass-green, grayish black; black if high in Nb–Ta | habit = Acicular to Prismatic crystals, elongated and striated parallel to [001] | twinning = Common on {011}, or {031}; as contact twins with two, six, or eight individuals, cyclic, polysynthetic | cleavage = {110} good, {100} moderate, parting on {092} and {011} | fracture = Uneven to sub-conchoidal | mohs = 6.0–6.5 | luster = Adamantine to metallic | refractive = nω = 2.613, nε = 2.909 (589 nm) | opticalprop = Uniaxial (+) | birefringence = 0.296 (589 nm) | pleochroism = Weak to distinct brownish red-green-yellow | dispersion = Strong | other = Strongly anisotropic | streak = Bright red to dark red | gravity = 4.23 increasing with Nb–Ta content | density = | melt = | fusibility = Fusible in alkali carbonates | diagnostic = | solubility = Insoluble in acids | diaphaneity = Opaque, transparent in thin fragments | impurities = Fe, Nb, Ta | references = }}

Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite.