RUTILE

Rutile is a titanium dioxide (TiO2) mineral and represents the most prevalent natural form of this compound. There are less common polymorphs of TiO2, such as anatase, akaogiite, and brookite. Known for its exceptional optical properties, rutile boasts one of the highest refractive indices among crystals at visible wavelengths, along with significant birefringence and high dispersion. These characteristics make it valuable in the production of specific optical components, particularly in polarization optics for longer visible and infrared wavelengths, extending to approximately 4.5 micrometers. Natural rutile can contain up to 10% iron, along with notable quantities of niobium and tantalum. The name rutile is derived from the Latin word rutilus, meaning 'red,' which refers to the deep red hue seen in some specimens under transmitted light. The mineral was first identified in 1803 by Abraham Gottlob Werner, who used samples sourced from Horcajuelo de la Sierra in Madrid, Spain, which is recognized as the type locality.