Opals, with their mesmerizing play of color, are a favorite among gem enthusiasts. However, some opals, particularly those from Ethiopia, require special care to maintain their beauty and stability. This article delves into the water sensitivity of Ethiopian opals and provides practical advice on how to prevent cracking and color loss.
Ethiopian Opal. Source: Wikipedia
Understanding Ethiopian Welo Opal
The Ethiopian Welo opal has some very unusual characteristics. Most notable is its hydrophane property, which means it has an ultra low water content and can actually act like a sponge and absorb water - as much as 10% of its weight. Most Ethiopian opal is "crystal" opal, which refers to its translucent to transparent body color rather than physical composition. The "honeycomb" pattern is the most rare and highly desired, and is unique to Ethiopian opal. This opal exhibits a subtle columnar webbing pattern within the host stone which produces a striped pattern if cut on the side, and the honeycomb pattern when cut across the "top". The honeycomb pattern itself can range from a very small, orderly arrangement of cells to large, irregular cells. Ethiopian opal is the only opal that displays a "rainbow" flash in which each patch of color is actually a full spectrum of color.
Prior to 2008, opal had been discovered in the Shewa province of Ethiopia. Although that material is beautiful, it is very unstable and the vast majority of it develops cracks and can literally break apart. This early material gave “African opal” a bad name.
The Discovery of Welo Opal
The 2008 discovery of a new deposit, in the Welo province in the northern part of the country (hence the name "Welo opal"), quickly brought out the naysayers who claimed that this new material, too, was not stable. The reality is that at the time, nobody really knew how stable - or not - this material actually was. 17 years into the discovery, this opal, once cut and polished, has turned out to be just as stable and durable as Australian opal.
Read also: Ethiopian Cuisine: Philadelphia Guide
How To Dry Your Ethiopian Welo Opal to Prevent Cracking Learn Lapidary Opals Cabbing Cutting
The Hydrophane Property
Ethiopian Welo opal has some very unusual characteristics. Most notable is its hydrophane property, which means it has an ultra low water content and can actually act like a sponge and absorb water - as much as 10% of its weight. Opal has varying degrees of water in it, and traditional belief is that the higher the natural water content, the less stable the opal. When Ethiopian Welo opal is immersed in water, it will soak up the water. As it does so, the opal’s color will first become very vivid, but as the saturation process continues, the opal will become completely transparent and the color disappears. As the opal begins to dry, it will first become very milky and opaque, and over the coming days - and in some cases weeks - it will gradually return to its original body color, color play, and degree of translucency.
Welo Opal Hydrophane Properties. Source: Opal Auctions
The Risk of Crazing
Opals are very sensitive to sudden changes in temperature. Opals do have significant water content (sometimes as high as 21%). If they dry too quickly they may indeed crack. This is also known as "crazing." That's why they're sometimes kept in water until they can be sold. This is also a way to hide flaws.
Practical Tips for Maintaining Ethiopian Opals
Here are some practical tips to help you care for your Ethiopian opals and prevent damage:
- Acclimation: If you purchase opals that have been stored in water, you'll need to dry them slowly. Before you take your opals to a gem cutter or jewelry maker, you'll have to dry them carefully and slowly.
- Slow Drying: Take the opals out of the bottle but don't dry them. Put them in a zip lock bag and then put that somewhere that isn't too hot. Leave them there for six months to a year before taking them to a lapidary or jeweler.
- Storage: When you store your finished stones, keep them away from sources of heat or cold and store them in soft, moist cotton. It's not necessary to store them in water, oil, or glycerin. Your opals will be fine as long as you don't subject them to sudden changes in temperature or rough handling. You can consult our opal care guide for more information.
- Avoid Prolonged Contact with Liquids: It is important for jewelry artists who use these opals to educate their customers - Ethiopian opal is a dynamic stone and care should be taken to avoid prolonged contact with water or other liquids, oils, soaps, or even perspiration!
Treatments and Stabilizing Techniques
Several methods have been suggested to stabilize Ethiopian opals and prevent color changes:
Read also: Authentic Ethiopian Cuisine
- Opticon Treatment: You might try drying the stone to get all of the water out, then immersing in "opticon", and then heating/sealing/hardening the stone and polishing/buffing the display surface. The opticon is both a fracture sealer and a hardener, it comes in a two part kit. We would put the opals in a glass jar with the opticon in it and heat it in a pan of water on the stove, repeat, then put the lid on until cooled. After that we wiped off the excess and put the hardener on.
- Glycerol Storage: If you store it in a bottle/container of glycerol, it will tend to not dehydrate.
- Coatings: Australian opal is much more stable than my Ethiopian from what I gather: much less susceptible to changes in the amount of water incorporated into the structure. If it were my piece of opal, I would use marine varnish as this stands up really well to water absorption or loss. Try clear lacquer, rather than varnish. It will protect and give a wet look without yellowing.
A word to the Wise: BEWARE of unscrupulous dealers who sell treated or dyed stones and fail to disclose them as such!! Since this opal is so porous, it can be smoke-treated to significantly darken its base color to make it appear "black", or dyed to alter the base color. Treated stones should ALWAYS be represented as such, and will always command a lower price than an untreated stone!
Additional Considerations
Several factors can influence the stability and appearance of Ethiopian opals:
- Lighting: I have always known that bright light is harmful to opals because of the hydrous nature of the beast. Opals worn for a long time never look as colourful as they did when new.
- Directionality of Color Play: As to your opal, what is the directionality of the play of color in relation to the light source? Is it "head on" fire (light passing over your shoulder from directly behind you with the opal in front of you) or is it a type of contraluz (opal between you and the light source, or at somewhat of an angle, with the light passing through the stone? If it is a contraluz type it is likely to only show color when immersed in liquid (water, glycerine, etc).
Summary of Care Recommendations
Here is a summary table of the recommendations for caring for Ethiopian Opals:
| Issue | Recommendation |
|---|---|
| Drying too Quickly | Dry slowly in a zip lock bag over 6-12 months |
| Storage | Keep away from heat/cold, store in moist cotton |
| Contact with Liquids | Avoid prolonged contact with water, oils, soaps, perspiration |
| Maintaining Color | Consider opticon treatment or glycerol storage |
| Coatings | Try marine varnish or clear lacquer |
Opal Care. Source: Fire and Ice
By understanding the unique properties of Ethiopian opals and following these care tips, you can ensure that your precious gemstones retain their beauty and value for years to come.
Read also: A Taste of Ethiopia in South Carolina
