Rutile in the context of "Titanium"

An oxide (/ˈɒksaɪd/) is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O ion with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al₂O₃ (called a passivation layer) that protects the foil from further oxidation.

Hafnium is a chemical element; it has symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1922 by Dirk Coster and George de Hevesy. Hafnium is named after Hafnia, the Latin name for Copenhagen, where it was discovered. The element is obtained only by separation from zirconium, with most of the world's hafnium production coming from processes that also produce zirconium. These processes make use of heavy mineral sands ore deposits, which include the minerals zircon, rutile, and ilmenite, among others.

Hafnium is most often used in alloys with nickel, and was used in larger quantities to produce the control rods used in nuclear reactors. Hafnium's large neutron capture cross section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors. It is ductile, and is also used in filaments and electrodes. Some semiconductor fabrication processes use its oxide for integrated circuits at 45 nanometres (1.8×10 in) and smaller, and superalloys used for special applications can contain hafnium in combination with niobium, titanium, or tungsten.

Sand mining is the extraction of sand, mainly through an open pit (or sand pit) but sometimes mined from beaches and inland dunes or dredged from ocean and river beds. Sand is often used in manufacturing, for example as an abrasive or in concrete. It is also used on icy and snowy roads usually mixed with salt, to lower the melting point temperature, on the road surface. Sand can replace eroded coastline. Some uses require higher purity than others; for example sand used in concrete must be free of seashell fragments.

Sand mining presents opportunities to extract rutile, ilmenite, and zircon, which contain the industrially useful elements titanium and zirconium. Besides these minerals, beach sand may also contain garnet, leucoxene, sillimanite, and monazite.

Anatase is a metastable mineral form of titanium dioxide (TiO₂) with a tetragonal crystal structure. Although colorless or white when pure, anatase in nature is usually a black solid due to impurities. Three other polymorphs (or mineral forms) of titanium dioxide are known to occur naturally: brookite, akaogiite, and rutile, with rutile being the most common and most stable of the bunch. Anatase is formed at relatively low temperatures and found in minor concentrations in igneous and metamorphic rocks. Glass coated with a thin film of TiO₂ shows antifogging and self-cleaning properties under ultraviolet radiation.

Anatase is always found as small, isolated, and sharply developed crystals, and like rutile, it crystallizes in a tetragonal system. Anatase is metastable at all temperatures and pressures, with rutile being the equilibrium polymorph. Nevertheless, anatase is often the first titanium dioxide phase to form in many processes due to its lower surface energy, with a transformation to rutile taking place at elevated temperatures. Although the degree of symmetry is the same for both anatase and rutile phases, there is no relation between the interfacial angles of the two minerals, except in the prism-zone of 45° and 90°. The common octahedral crystal habit of anatase, with four perfect cleavage planes, has an angle over its polar edge of 82°9', whereas rutile octahedra only has a polar edge angle of 56°52½'. The steeper angle gives anatase crystals a longer vertical axis and skinnier appearance than rutile. Additional important differences exist between the physical characters of anatase and rutile. For example, anatase is less hard (5.5–6 vs. 6–6.5 on the Mohs scale) and less dense (specific gravity about 3.9 vs. 4.2) than rutile. Anatase is also optically negative, whereas rutile is optically positive. Anatase has a more strongly adamantine or metallic-adamantine luster than that of rutile as well.