Understanding Emerald Enhancements and Treatments


emerald enhancements - jardin
Illuminated from behind, this emerald reveals its jardin of fractures and inclusions. “Emerald” by Mauro Cateb. Licensed under CC By 2.0.

Since emeralds are almost always included, they frequently receive a variety of gemstone treatments to increase their visual appeal. Emerald enhancements may involve numerous types of fillers, impregnations, and dyes. Gem cutters, jewelry makers, and vendors do this to make an emerald’s jardin more pleasing. French for “garden,” the term refers to the lovely inclusions typically found in these gems.

Almost all emerald enhancements can cloud over time. So, whether you’re treating a stone for the first time or re-treating a discolored gem, follow these procedures.

Cleaning Emeralds

First, clean the emerald thoroughly. Warm conditions help the cleaning process. If you warm both the stone and the cleaning liquid or filler together, you’ll open the stone’s pores. This will allow deeper penetration.

Don’t boil the emerald or immerse it in hot liquid. You’ll crack or shatter the stone.

A simple overnight soak in a jar of the cleaning medium on a hot plate may be enough to clean the emerald. (Again, warm conditions, not hot).

Organic Solvents

You can use organic solvents. Organic solvents safe for use with emeralds include:

These preparations can evaporate in air and leave a residue worse than the original problem. Therefore, use a covered container.

Acids

If the organic solvents don’t remove the contaminants, you can use acids. For an intense cleaning, try aqua regia, a mixture of one part nitric acid to three parts hydrochloric acid. Please note: hydrochloric acid fumes are toxic. Just the slightest whiff will burn your nose.

If your emerald has orange or brown rust stains, you can remove them with a solution of oxalic acid.

Exercise caution when using and disposing of these acids. Read and follow the instructions and safety guidelines for any acid products you purchase.

After an acid treatment, wash the stone with warm soap and water. In some cases, bathe the stone in a neutralizing solution. Some acids can have a delayed discoloring chemical reaction. You must neutralize them with solutions like baking soda and water. Consult a mineral cleaning expert for details.

Emerald Enhancement Procedures

After cleaning the emerald, let it dry thoroughly. Now, you have two options. Simply soak it overnight again, this time in a container on a hot plate with a warm filling/penetrating solution. Or, you can try the more effective vacuum method.

Place the stone in a vacuum and insert the treatment medium while still under the vacuum. Do this under mild heating as well. It will open the stone’s pores and drive off any remaining water. In some cases, the filler medium needs mild heat just to stay liquid.

You can construct a simple vacuum chamber inexpensively. You’ll need a plastic or glass bell jar type cover, a hot plate, and a hydraulic piston assembly. If you can’t find one online, auto supply stores will carry the parts you need to build the hydraulic force feed. The assembly should look something like the following image.

emerald enhancements - vacuum chamber

Choosing Fillers for Specific Emerald Enhancements

To determine the filler substance you should use, you must consider several factors. First, think about why you’re treating the emerald in the first place.

Cracks and Inclusions

If you want to disguise cracks and inclusions in the emerald, use a material with a refractive index (RI) close to the stone’s. Consult the chart below.

Refractive Indices of Common Gem Fillers

Fillers RI Natural Stones RI
Coconut oil, paraffin wax 1.45 Quartz 1.55
Neat’s foot oil, whale oil, Corn, mineral, olive, peanut 1.46 Beryl, Emerald 1.58
Rapeseed & soybean oil 1.47 Topaz 1.61
Caster oil, linseed oil 1.48 Ruby, Sapphire 1.77
Lubricating oil 1.49 Diamond 2.42
Cedarwood oil 1.51
Canada Balsam 1.53
Opticon 1.54
Epoxy No.224 1.54
“ExCel/Gemtrat” 1.53
Polymers (epoxies) 1.5-1.6
Glass 1.5-1.9
Palm oil 1.57

Fissures and Pits

Blemishes like fissures or pits that break the surface of the emerald may require a thicker filling agent.

Color

For a pale or color-zoned emerald, consider a coloring additive to give the gem a richer, more even color. You can use any number of dyes, including chromium powder. If you can find it, a ready mix sold in Bangkok as “Crown of King” emerald oil contains both the oil and dye. As an added effect, an emerald permeated with chromium powder will have a nice red glow under ultraviolet light or an emerald or Chelsea filter.

Long-Term Effects of Common Fillers for Emerald Enhancements

Keep in mind the long-term effects of filler media when making your choice.

Cedarwood Oil

Used very frequently for emerald enhancements, cedarwood oil discharges quite rapidly. A thicker application won’t delay this effect. Also, when exposed to ultraviolet light, this oil emits oxygen as a by-product, which can stain.

Canada Balsam

The North American balsam fir (Abies balsamea) produces this oleoresin. It makes an excellent filler due to its thickness, even in a liquid state when heated. However, this organic material can decay and discolor over time. Adding toluene to thin the material for better penetration can slow this. Canada balsam is often sold with additives to prevent this deterioration. (You can also use this substance as an adhesive for microscope slide covers).

Opticon

This lapidary fracture filler works well, with one drawback. Opticon contains a sealer that breaks down after a year, starts oxidizing, and turns yellow. However, it sets hard enough to polish.

Palm Oil

Palm oil or Palma (a synthetic derivative of Epoxy 828 or 6010) clouds to a milky color in the long term.

Solder Glass

This makes an excellent filler, similar to that used in the Yehuda clarity enhancement for diamonds. With a melting temperature of 250° C, solder glass is used in the electronics industry. You can also use colored solder glass.

Beeswax

One of the simplest fillers, beeswax gives an excellent finish and luster to the stone. You can apply it after all treatments or by itself to fill minor pits.

Vaseline

Long lasting Vaseline or mineral oil (liquid paraffin) won’t discolor.

Water Glass

Sodium silicate makes an excellent filler, doesn’t discolor, and sets hard enough to polish.

Other Fillers

Epoxy No.224 plus hardener turns yellowish orange over time.

Dental fillers and epoxy-based adhesives that set up with ultraviolet light apparently don’t discolor.

“ExCel” (formerly referred to as “Gemtrat”) is a proprietary epoxy resin and hardener process created by Arthur Groom and Co. It’s permanent and colorless.

Other Emerald Enhancements

Irradiation

Radiation treatments appear to have no effect on emeralds. In one study, crystals from Colombia and Australia were irradiated, both as natural crystals and after a bleaching to white by heating to destroy the color centers. You’d expect these emeralds to turn yellow, at least. After all, irradiation commonly does this to most beryl gems. However, this limited experiment produced no changes.

Lasers

A laser will remove black spots. However, it will also leave a black trail where it burns through the stone. An emerald can withstand lasering but will shatter in a heated acid bath to remove the trails.

Mark Liccini

Gemstone Rough Dealers since 1970

emerald enhancements - cut gems
“Cut Emerald Stones” by Irvin Calicut. Licensed under CC By-SA 3.0.

About the author
Mark Liccini
The late Mark Liccini began his career as a stone carver in the 1970s and worked for many decades as a renowned lapidary. Mark mastered the art of gemology, gaining degrees from Gemmological Association of Great Briton,and Columbia School of Gemmology, Wash.D.C.
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