A synthetic gemstone of the same composition as natural rutile but of different appearance. It has been produced since 1948 by a modification of the flamefusion process of the Verneuil Furnace. The resulting boules are opaque black, but when reheated in a stream of oxygen they change to various colours. Thevariety most in demand commercially is pale yellow to colourless, resembling a diamond but distinguishable by its colour, greater fire, much higher colourdispersion, lower hardness, and having strong double refraction. It has been sold under many trade-names, e.g. Titania, Titangem, Diamothyst, Titanstone, etc., or the misnomer 'Rainbow diamond'. Ithas been largely superseded by synthetic strontium titanate which is whiter.