Many natural stones today are treated to improve their appearance and saleability. In order to supply a mass market with high quality material, a number of gemstones are routinely heat treated to improve or change their colour. Some are irradiated, in a process that mimics the effect of natural radiation in the earth. As long as the treatment is permanent and within safe limits, disclosure is usually not considered obligatory. However, certain new practices, among them laser drilling of diamonds, fracture filling of diamond, emerald and ruby, and diffusion treatment of ruby and sapphire are more controversial. They should always be disclosed at the point of sale and prices should be correspondingly lower. Some treated stones need extra care with cleaning and wear.
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