Published: July 2012
This treatment has been applied for centuries. Originally done with beeswax, it can improve the luster, texture and clarity of a gem. While paraffin wax is more commonly used today, beeswax is still used in some traditional methods, such as jade carving in Myanmar (Burma). The wax is applied as part of the polishing process with much rubbed off of the gem, but some adheres to surface pits and cavities improving the finish and surface texture. Waxing usually adds a subtle, rather than a dramatic change to a stone and is primarily used on translucent or opaque gems. Coral is commonly waxed, but more porous varieties may have more modern treatments applied. Most waxes are colorless, but can have color added. Some stones may have residues from polishing compounds trapped in surface pits or hollow growth tubes. This is common in bead materials and is generally not considered a treatment, as it is not intentional, nor does it alter the appearance or value in any significant way.
This treatment has been applied to emeralds for thousands of years. Ancient texts describe the process often using locally sourced vegetable oils. Emerald is most associated with this treatment, as it commonly has inclusions which are easily minimized by oiling, but any gemstone with surface-reaching fissures or cracks can admit oil. The presence of the oil replaces the air and optically makes the feature less noticeable. Modern methods generally use synthetic resins or polymers, the modern counterpart to oils. Cedar wood oil and Opticon are commonly used polymers. Closely related to these are paraffins. Lab gemologists refer to all of these as polymers, and they all have the same result when used: they reduce the appearance of cracks and open inclusions. Different polymers are used for different materials because they try to match the optical properties of the gem being treated. The more closely the optical properties match, the more effective the treatment. Liquid polymers can be removed when a gem is cleaned, and they can deteriorate and dry out with time. As a result, these treatments need to be periodically reapplied, and care must be taken when cleaning such gems so the polymer is not removed. There are newer treatments that use polymers, but add a hardening process to make them more permanent. These can only be removed by very powerful solvents, and are considered semi-permanent and stable.
There are a number of beautiful gems that are not suitable to be worn as gems without a little help. Some have a delicate structure, some have a rough texture that needs smoothing, some need to maintain a delicate chemical balance, some are brittle and some are porous. The term “impregnation” is sometimes substituted for “stabilized”, but in most cases will indicate the same type of treatment.
Turquoise is the best known of the stabilized gems. Turquoise is made up of multiple microscopic individual crystals of a hydrous copper phosphate. Depending on how they formed, there is a range of porosity to the material. This porosity allows turquoise to absorb any fluids or oils to which it is exposed, which can alter the color of the gem over time. This is why old turquoise commonly appears greenish in color. The main sources of American turquoise today produce a turquoise that is more porous, giving it a chalky appearance if not treated. Further, it is easily broken and attacked by acids and other chemicals, so stabilization is usually a necessary and desired treatment for this material.
The earliest known form of stabilizing was with beeswax. It was a common part of the final polish on gems like jade, but was also important for smoothing the surface pits and natural channels in materials like coral. Paraffin wax gradually replaced beeswax, with only some jades receiving this treatment now. Paraffin was harder and more durable, but always vulnerable to heat. In the 20th century, polymers were developed that had all the benefits of waxes without the problems. These polymers can permeate a material and then be hardened. The result is a material that is structurally stabilized and resists fluids and other potentially damaging substances.
Like dyes, not all material will accept stabilization and some only under certain conditions. The delicate structure and fragility of natural turquoise make it ideal to stabilize. Indeed, there is a premium in the market for superior stabilization processes. While these do not add any color, the result is often a better-perceived color. Much as a wet material appears darker, a stabilized turquoise will have better color than before treatment. Some materials might be both stabilized and dyed, and in such cases, both treatments should be disclosed.
Many corals and materials with an open structure benefit from stabilization with plastics to seal up these large openings that may feel rough or be prone to gathering dust and particles. Shell can be naturally porous and soft. Stabilizing it with a polymer gives it a protective coating. Most materials that can be commonly dyed can also be stabilized or impregnated, as it requires a degree of porosity. Polymers are often combined with other treatments such as color enhancements.
Less expensive jades can be treated with acids to remove impurities and the remaining voids filled with a polymer. This process produces what is known as B-Jade. It is frequently accompanied by dyeing and improves both the clarity and color of the jade. These treatments should be separately disclosed.