Gemstone Treatments (Enhancement)

  • Enhancement and treatments are done on gemstones to improve their appearance, properties and consequently their value. This is generally practiced on lower grade goods so as to increase their salability.
  • In actual terms, improvements in a gem material may be specifically related to improvement in Colour and / or Clarity and / or Phenomenon and / or Durability. In some cases a stone is subjected to more than one form of treatment.
  • A number of classifications have been put forward by ICA, GIA, CIBJO, jewelers associations in different countries etc. As yet no single classification is considered as a standard.
  • The terms enhancement and / or treatment are used ambiguously by members of the trade, though there is a general concept that the acceptable ones such as oiling may be considered as an enhancement while glass fillings, irradiation etc. as a treatment. The technical concept remains that - whether you call it enhancement or treatment - they basically mean the same.
  • The important factor is that total disclosure of whatever has been done to the stones is absolutely necessary and is the general attitude of most jewelers these days.

Basic definitions of possible enhancements / treatments are as follows:

  1. Bleaching: The use of chemicals or other agents to lighten or remove the colour of a gemstone.
  2. Coating: The use of such surface enhancements as lacquering, enameling, inking, foiling or sputtering of films to improve appearance, provide colour or add other special effects.
  3. Colourless impregnation:
    • The filling of surface breaking cavities or fractures usually with colourless oil, wax, plastic, natural or synthetic resin (with or without hardeners), other man-made materials and glass, to improve durability and appearance.
    • The use of a colourless bonding agent (wax, polymers, plastic etc.) within a porous gemstone to give it durability and improve appearance.
  4. Coloured impregnation (Dyeing): The use of colouring matter to improve the colour by darkening the original colour or improve colour uniformity in stones containing surface reaching fractures and cavities, or in porous gemstones.
  5. Lasering or Laser drilling: The use of a laser and chemicals to reach and alter inclusions in diamonds.
  6. High Pressure High Temperature (HPHT): The use of a variety of high-temperature annealing techniques at different pressures to enhance optical properties such as the colour and brilliance of certain types of diamonds.
  7. Graphitization: The use of high temperature on poor quality yellow to brown diamonds to change the colour to black.
  8. Heating: The use of heat to effect desired alteration of colour, clarity and / or phenomena.
  9. Irradiation:
    • The use of gamma and / or electron bombardment to alter a gemstones color may be followed by a heating process.
    • The use of neutron bombardment, with the combination of any other bombardment and /or heat treatment to alter a gemstone's colour (In U.S.A. such stones require an environmental safety release from the Nuclear Regulatory Commission).
  10. Diffusion: The use of chemicals in conjunction with high temperatures to produce colour and / or asterism - producing inclusions.

The techniques are explained with respect to the nature of the gemstone being enhanced, the materials used, the possible effects and the general identification of the enhancement.