Rutile

Rutile* is a mineral composed primarily of titanium dioxide, TiO2.
Rutile is the most common natural form of TiO2. Two polymorphs of TiO2 are known:Anatase (sometimes known by the obsolete name "octahedrite"), a tetragonal mineral of pseudo-octahedral habitBrookite, an orthorhombic mineralRutile has among the highest refractive indices at visible wavelengths of any known crystal, and also exhibits a particularly large birefringence and high dispersion. Owing to these properties, it is useful for the manufacture of certain optical elements, especially polarization optics, for longer visible and infrared wavelengths up to about 4.5μm.
Natural rutile may contain up to 10% iron and significant amounts of niobium and tantalum. Rutile derives its name from the Latinrutilus, red, in reference to the deep red color observed in some specimens when viewed by transmitted light.
In large enough quantities in beachsands, rutile forms an important constituent of heavy minerals and ore deposits. Miners extract and separate the valuable minerals e.g., rutile, zircon, and ilmenite. The main uses for rutile are the manufacture of welding rods, refractory, ceramics, as a pigment, and for the production of titanium metal.