– the surface of a porous gemstone is permeated with a polymer, wax or plastic to give it greater durability and improve its appearance.
The most commonly encountered wax or plastic impregnated gemstones are opaque, and they include turquoise, lapis lazuli, jadeite, nephrite, amazonite, rhodochrosite and serpentine.
Porous gem materials such as this pale turquoise on the left is impregnated with a wax or polymer substance, which caused the material to deepen in color and become more stable.
1. Durability factors – Many impregnations are often “skin deep” and due to the melting point of plastic and wax, can be susceptible to heat damage. Plastic impregnations are considered durable in gem materials such as turquoise as long as they are not subjected to heat or chemicals.
2. Detectability – In most instances a qualified gemologist can readily identify the treatment.
3. Encountered in the trade – Frequently seen in the trade.
4. Special care requirements – Care must be taken not to subject gemstones with wax or plastic impregnations to heat, such as that encountered by a jeweler’s torch, since these will likely damage the material.
Source: Robert Weldon, www.gia.edu
To learn more about gem treatments see also: