When pure, titanium dioxide is relatively clear and has an extremely high index of refraction with an optical dispersion higher than diamond. It is produced artificially for usr as a gemstone, but it is relatively soft. Star sapphires and rubies exhibit their asterism as a result of the presence of TiO2. Titanium dioxide is extensively used for both house paint and artist's paint, as it is permanent and has good covering power. Titanium paint is an excellent reflector of infrared, and is extensively used in solar observatories where heat causes poor seeing conditions.
Titanium tetrachloride is used to iridize glass.
This compound fumes strongly in air and is used to produce smoke screens. Its use is growing rapidly, and by 1978, it is expected that 10 million pounds of the metal will be used.