What does synthetic opal look like?

Treated opals (continuation of the article “Types of opals”).

Opal can undergo various types of treatment (enhancement). These CIBJO guidelines state that any processing method other than standard cutting and polishing must be disclosed and the process used stated on all invoices, advertising and sales documents. Types of treatment include color and/or tone enhancement (Figure 12), heat, dyeing, resin and wax, smudging, or any application of chemicals. Opal is treated to alter its natural appearance or strength. The body tone of the opal is often enhanced (usually made darker) in some opal inlay jewelry by painting a thin slab of solid opal crystal with black paint, or mounting the slab with black glue, or by setting it into the jewelry on a black base.

Figure 12. Treated (carbonized) dark Andamooka opal matrix dies. (Photograph, R. Weber).

Composite natural opal.

Composite natural opal consists of natural opal laminates hand cemented or bonded to another material. The opal component is natural opal. There are three main forms of compound opal: Doublet Opals are a two-part composition where a piece of natural opal is cemented onto a base material (Fig. 13A).

Rice. 13A. Cylindrical black duplex duplex type Lightning Ridge. (Photograph, G. Brown).

Triplet opals are a three-piece composition where a thin piece of natural opal is cemented between a dark base material and a clear top layer (usually quartz or glass). In triplets, a protective layer of high-quality quartz glass gives the stone additional advantages: the glass lens visually magnifies the individual details of the semi-precious pattern (Fig. 13B).

Rice. 13V. Scheme of opal composites.

Mosaic and chip opals are a composition of small flat pieces of irregularly shaped natural opal, cemented like mosaic tiles on a dark base material (Fig. 14A, 14B), and filled with resin.

Figure 14A. Mosaic dark opal composite. (Photograph, R. Weber).

Rice. 14 B. Mosaic opal ring.

Synthetic opal (Figure 15A) is a material that has essentially the same chemical composition and physical structure as natural opal, but has been manufactured in a laboratory or industrial manner. Synthetic opal composites also exist as synthetic opal doublets, triplets or mosaics. In this case they should be classified as synthetic opal composites (Fig. 15B). A well-known manufacturer of synthetic opals for jewelry is the Gilson ™ company. The company creates imitations of opals of all categories: from scarce black to ideal white, recognized as the most sophisticated. The affordability, variety of colors and beauty of such opals, combined with higher hardness, make synthetic opals very attractive to consumers.

Fig. 15A. Gilson™ synthetic black opal. (Photography, G. Brown)

Fig. 15B. Black synthetic Gilson™ aromatic doublet. (Photography, G. Brown)

Imitation opal is a material that imitates the play of color of natural opal, but does not have the same physical and chemical structure or gemological constants as natural opal (Fig. 16). Opal is an expensive stone, so not every buyer can afford jewelry with it. But in order not to deprive fashionistas of the opportunity to show off products with unusual minerals, scientists came up with synthetic opal.

Properties of opals of different origins

• resistance to external influences;
• spectacular look;
• difficult to distinguish from natural mineral;
• The stone is insensitive to low humidity.

For those who have not yet purchased opal, it will be useful to know that the price difference is large. If natural opal is purchased from $100 per carat, then a synthetic stone will cost a hundred times less, and the iridescence looks just as impressive.

The characteristics of the two stone options differ slightly from each other:

• the density of synthetic opals is lower (2,05 compared to 2,10);
• The hardness of artificial stones is also slightly lower (4 versus 5,5 on the Mohs scale).

These properties affect the wear resistance of the substance, but in everyday life it is impossible to distinguish or feel them. There are also differences in the external effects that opal creates. Thus, phosphorescence is shorter in time for synthetic stone. If you study the structure of iridescent spots, you can also find differences in it. Synthetic stones have a similar appearance to the skin around a scar, which gemologists call the “lizard skin” effect.

There are also differences in structure. Natural opals are not porous, so they do not stick to the tongue, but you can check this if the opal is already at home. Real opal also has a different refractive index, so a gemologist can distinguish a fake using a refractometer. You can also find differences by determining the specific gravity of a substance.

Possibilities of working with opals

In recent decades, the jewelry industry has stepped forward. Not only was a synthetic mineral invented, natural stones also began to be refined. Such a mineral cannot be called completely artificial, but its cost is still cheaper than that of natural stone. There are several methods for processing stone, but store sellers do not always report them:

1) Making doublets.

Doublets are a type of stone in which the upper part consists of a single piece of opal, most often natural. But the lower part is a black base made of ordinary stone. The name fully reflects the dual structure of the substance. Externally, the stone looks like real black opal.

A glued specimen is easy to recognize, especially since the natural layer of opal is very thin; sometimes such stones are visible in photographs. If you look at the opal in profile, you can see the structure of the doublet with the naked eye. The cost of stone is 20 times cheaper than natural stone.

Triplets are also substances obtained by gluing layers together. Real stone is present in the composition, but only as a plate between the transparent dome and the black backing. Of course, the cost of such specimens is even cheaper than natural stones or even doublets. Iron stone serves as the base, and iridescence also appears. But it’s easy to distinguish a triplet – you just have to look at the stone in profile, where three layers will appear.

3) Impregnation with smoke.

Ethiopian opals are used as raw materials. It is these that sellers most often pass off as natural, and therefore do not warn about the origin of the stone. Such schemes can be found on the Internet or in small jewelry stores, as well as when purchased from private traders.

The essence of the method is that the structure of the stone is slightly porous, and during smoke treatment, soot particles penetrate inside the substance. The mineral itself becomes black, and the opalescence effect increases. The brightness and color of the opal increases. The smoke impregnation method is easy to use and the properties of the mineral do not change. It can be calculated by a gemologist by examining the stone under magnification.

But sometimes you can guess for yourself, especially if jewelry store sellers indicate the country of origin – Ethiopia. Black opals are not found there; all stones brought from there with this shade are ennobled by smoke.

4) Coloring with synthetic dyes.

The easiest way to change the type of stone. Painting is also the cheapest option for refining; painting can be done in any color. But often the saturation of the shade, its uniformity and unnatural brightness lead to thoughts about the artificiality of the specimen.

Jewelry with synthetic opals

Artificial specimens

Fully synthetic opals are divided into two types, depending on the manufacturer:

• Gilson opal is one of the varieties of synthetic opal produced by the company of the same name. Such specimens are the most sophisticated on the artificial stone market. The conditions in which the stone is produced are close to natural, but accelerated in time. The entire process of obtaining a copy lasts up to eighteen months. The colors of the stone do not appear through pigments added to the structure, but as a result of diffraction. And such opal costs no more than $1 for a medium-sized stone.
• Keutzer opals are stones that are identical in composition to natural opals. But the company is famous for the fact that specimens are impregnated with special rubber, which allows the stones to last longer. Such substances have not only greater hardness, but also fewer inclusions in the structure. Rubber is added at the production stage, it is colorless and does not affect the appearance.

It was these two companies that practically divided the artificial opal market. Sometimes sellers themselves do not know about the origin of the opal, but there is a high probability that the stone originated from one of these companies. It often happens that sellers hide their synthetic origin due to the large difference in price. It is not easy to distinguish specimens, but to do this quickly and reliably, you should contact a gemologist. You can suspect a fake by its appearance if the stone has a very regular pattern or high brightness with low cost.

The properties of stones of different origins differ. This also affects the magic of the mineral. Of course, artificial substances do not provide any benefit to the owner, lithotherapists do not use them, and one should not expect a positive effect after use. The power of doublets, triplets and enriched opals is reduced, but any zodiac sign can wear such stones and not worry about the impact on character and life.

On the market and in jewelry stores, most stones are either synthetic or refined. Therefore, you need to request documentation from the seller, find out about the origin of the opal and check the cost. In any case, you can choose opals according to your budget and your own taste. The fashion for stone will not go away soon, but now you can surprise with such decoration.