Chatham, as used in gemological conversation, stands for a manufacturing technique of synthetic gemstones. The method incorporates crystallization of a gem material from a solution in a flux rather than from molten ingredients such as the flame fusion or Czochralski method. Its inventor, Carrol Chatham, tried to mimic the situation (certain) gems form in nature. Deep in the earth’s crust temperatures and pressures allow water to hold higher quantities of minerals in solution than at the surface of our planet. When these hydrous solutions rise, they cool and experience ever-decreasing pressure causing the chemical elements to come out of solution and crystallize to become gemstones and minerals as we know them. Bypassing the necessary immense pressures, Chatham used a flux to create supersaturated solutions.

Some important gem minerals that can (and are) produced by the flux-melt (or Chatham) method are:

• Corundum, (ie. ruby & sapphire)
• Beryl (ie. emerald)
• Chrysoberyl (ie. alexandrite)
• Spinel