The majority of gemstones on the market are routinely enhanced using a range of treatments. You should be aware of the effects these may have on the way you use the gemstones and also on how you can advertise and sell your jewelry.
If you advertise or sell jewelry, the claims – you make about your products must be accurate. Products must be described truthfully and any information about gemstone treatments disclosed to customers. It is advisable to buy your material from a reputable source and know how to recognize some of the treatments. Commonly used treatments include: heating, dyeing and staining, bleaching, coating, irradiating, impregnating, fracture filling and diffusion treatments.
There are a number of organizations, such as the Federal Trade Commission (FTC) and the World jewelry Confederation (CIBJO), that offer guidelines for the disclosure of treatments, describe the treatments and outline what is currently considered acceptable practice in the gem and jewelry trade.
The FTC states that “sellers should tell consumers about gemstone treatments … if the treatment is not permanent or if the treated stone requires special care”, and even when this is not the case, you should “tell consumers about the treatment if it significantly affects the value of the gemstone”. The FTC recommends the following disclosures:
•If the colour of a treated gemstone will fade over time, tell the consumer that the gemstone has been treated, that the treatment is temporary, and that the stone’s colour will fade over time.
•If ultrasonic cleaners or solvents should not be used to care for a treated stone, tell the consumer that the gemstone has been treated and the cleaners or solvents to avoid.
•If a diamond has been laser drilled to improve its clarity – but is then less valuable than a comparable diamond that has not been treated – tell the consumer the diamond was laser drilled.
Turquoise may be waxed, oiled or treated with resins to improve its appearance and keep it from drying out. It may also be stained to improve its colour.
Surface treatments, including waxing and inking, are not permanent and may be rubbed off. The stone’s surface may also be covered with a thin film or foil to enhance its appearance. A dye, stain or bleach may colour the surface leaving the centre unchanged, may follow along cracks and Haws, or may diffuse throughout the whole gemstone, changing colour, clarity and appearance.
Colourless and coloured waxes, oils, resins, plastic and glass are used to impregnate gemstones, filling cracks and flaws and improving appearance, which adds to the value. Turquoise is often waxed. Oiling of emeralds is such common practice that it is seldom disclosed. Natural oils and resins may “leak” over time, and emeralds should be reoiled regularly to avoid drying out and cracking.
Heating, irradiating and the use of laser
This is Heat treatments are common practice in the gem and jewelry trade, so much that you can assume all material has been heat treated in some way, unless it is described otherwise. Heating is used to change, lighten or darken the colour of a gemstone or improve its clarity. Heat treatments are generally permanent.
Irradiant treatments bombard gemstones with electrons or gamma rays to alter their colour. Diamonds can be irradiated to remove the yellow tinge and increase the colour grade and therefore the value. Topaz may be heat treated and irradiated to change brown opaque crystals to the bright blue topaz so popular in jewelry. Laser drilling is used to remove dark inclusions from diamonds, improving the clarity of the stone.