In the light colored stones and in white sapphire, the difficulty is greater, as there are no color variations in the latter case.
The author thus obtained a white sapphire from a crystal of light yellow material.
Few colorless stones other than diamond, white sapphire (chiefly scientific), and quartz are seen in the trade.
A regular series of changes is said to be produced in white sapphire by this means, the final color being yellow.
Clear, colourless crystals are known as white sapphire, and are very valuable.
It has been produced artificially by adding iron instead of chromium to the matrix from which the white sapphire crystallizes.