Gem Enhancement and Treatments

by Manisha G

Enhancement and treatments are done on gem materials to improve their appearance, properties and subsequently their value. This is generally practiced on lower grade goods so as to increase their salability. In actual terms, improvements in gem materials may be specifically related to improvement in color and/or clarity and/or phenomenon and/or durability. In some cases a stone is subjected to more than one form of treatment.

One of the crucial issues facing the gem and jewelry industry today is that of enhancement and treatments of gem materials. This is of paramount importance to India which is a major trading and supplier country. The ethics of whether treatments are acceptable or not is no longer the point, the fact whether they should be disclosed or not has taken precedence.


Basic types of possible enhancements and treatments are as follows;

1. BLEACHING: The use of chemicals or other agents to lighten or remove the colour of gem material.

2. COATING: The use of such surface enhancements as lacquering, enameling, inking, foiling to improve appearance, provide colour or add other special effects.

3. COLORLESS IMPREGNATION: The filling of surface breaking cavaties or fractures usually with colourless oils, wax, plastic, natural or synthetic resin (with or without hardness), other man made materials and glass to improve durability and appearance.

4. COLORED IMPREGNATION (DYEING): The use of colouring matter to improve the colour by darkening the present colour or improve colour uniformity in stones containing surface reaching fractures and cavaties or in porous gemstones.

5. HEATING: The use of heat to effect desired alteration of colour, clarity and/or phenomena.

6. LASERING: The use of laser and chemicals to reach and alter inclusions in diamonds.

7. IRRADIATION: The use of gamma and /or electron bombardment to alter the colour of a gemstone may be followed by a heating process.

8. DIFFUSION: The use of chemicals in conjunction with high temperatures to produce colours and/or asterism producing inclusions.

9. COMPOSITE STONES: A comprehensive term which includes doublets, triplets in which a stones consists of two or more parts either of the same or of different materials cemented or otherwise joined together.

10. FOILED STONE: A gemstone mounted with backing of silver or coloured foil to improve its brilliance or enhance its colour.

11. CHEMICAL VAPOR DEPOSITION (CVD): I is a process of diamond synthesis in which a thin film of tetrahedrally bonded carbon atoms are deposited on a substrate. It is done in the presence of hydrogen and methane in low pressure moderate temperature environment. Also called Plasma enhanced chemical vapour deposition.

12. FRACTURE FILLING: It is a process in which a wide variety of substances such as oils, waxes, polymers or glasses are used for filling of pores, fractures and even cavities in a gemstone.

13. HPHT TREATMENT: High pressure high temperature treatment is being done on diamonds to change brown colour diamond to colourless diamond as well as fancy pink, green diamonds.


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