How to recognise a natural gemstone from fakes and from its “test-tube brothers” the synthetics.
Up to now in our articles we have analysed the features that a fine gemstone must have in order to be considered a quality gem.
We presumed however that all the gemstones considered were natural.
Actually people have always tried to reproduce fine gemstones since ancient times.
The fakes produced can be summarised into three types:
coloured glass gems;
The use of coloured glass or composite materials is nothing new as the first fakes are dated back to ancient Roman times.
Artificial glass has different features compared to natural materials and thus it is easy to recognise.
Composite materials are known as “doublets” and “triplets”. They are called “doublets” when two pieces are cemented together by transparent cement and they are called “triplets” if three cemented pieces are used. Many different materials can be used.
I.e of Triplet
The last challenge: synthetic products
Synthetic gemstones are the latest product in the market: they are not actual fakes and I can give you a better idea if I talk about cloning natural materials. I used the word “cloning” because through a lab synthesis process, it is possible to create rubies, sapphires, emeralds and so on with the very same physical and chemical features of the natural gemstones. The minerals from which synthetic gemstones are cut are test-tube produced. Actually their production is not in vitro but sophisticated processes are used with high-temperature high-pressure autoclaves.
Sometimes these processes are very expensive, so the production is quite limited. For example similar synthetic products (not existing in nature) such as YAG, GGG, cubic zirconia and synthetic moissanite are preferred to more expensive synthetic diamonds.
Some people compare these products to vitamins: there are natural vitamins (obviously more expensive) and synthetic vitamins produced in a laboratory.
Synthetic vitamins and synthetic emeralds share the same chemical structure with their natural counterparts; that is why they are not just “fakes”.
Synthetic minerals are very difficult to recognize but some features are different from the natural!
There is of course a difference between the crystal produced by mother nature in billions of years and the crystal created by man in just a few weeks.
The first synthetic gemstones were put on the marketplace since 1800…so beware of granny’s jewels!
The first synthetic products were easily recognisable, while nowadays their perfection should give us a clue: they are too beautiful to be natural!
As we have already explained the chemical, physical and optical properties are similar to their natural counterparts and they can be recognised by experts. Anyhow we can give you some important clues.
Consider the rarity of a gemstone:
Synthetic products can be produced in any quantities and of any carat weights. Beware if the proposed gemstones are all similar, high quality and with a remarkable carat weight: natural gemstones with such features are not easily found and if so they will certainly differ in some features such as colour, shape, clarity etc.
Inclusions and fractures are not always detrimental:
Some natural materials generally have inclusions and fractures. For example, the inclusion of a small crystal in a ruby can tell us of its origin and its genesis. The total absence of inclusions should make people think especially when evaluating materials that come naturally with inclusions such as rubies and emeralds.
The aspect of the inclusions can be noticed when analysing a gemstone under a magnifying lens. Whitish opaque inclusions similar to one another that do not change colour when moving the gemstone or air bubbles should make us suspect it is a synthetic gemstone. This kind of inclusion is the remains of the fused material used to synthesize the crystal or gases that get trapped during the growing process. Another clue visible under a magnifying lens could be the growth lines i.e. curved lines within the crystal that cross all the facets of the gemstone. These lines are caused by the rapid growth of the crystal in the crucibles.
Beauty with no treatments:
99% of natural emeralds show inclusions and fractures. Most emeralds undergo at least one oil treatment to make the gemstone shinier.
Many gemstones such as sapphires and rubies undergo different treatments: fractures are filled with different materials in order to make them less visible. Synthetic products do not usually undergo treatments and do not show any of the features described above.
The colour of synthetic gemstones is usually too vivid to be true or those gemstones can be of many different colours as it is easy to produce specific colours; it may suffice to add colouring elements or chromophores for the specific mineralogical species to be produced.
Pay attention to details:
Shape, cut and polish care are other elements that should make us think about the possibility the gemstone is a synthetic.
Gemstones with a remarkable carat weight like emeralds are usually not available with a brilliant round cut; the same thing happens with other gemstones that usually have an oval or mixed cut.
The cutter often modifies the classic cut to use as much rarough mineral as possible and enhance its colour: this causes a non-symmetrical cut.
Synthetic gemstones do not usually need such care. Also polishing of the facets is not carried out with the same attention in synthetic products, so flaws are often visible on the surface under magnification.
Synthetic gemstones are usually sold at very tempting prices and these gemstones are usually very beautiful, but beware of the bargain!
For example a beautiful synthetic ruby with a beautiful red colour without inclusions should cost about ten times less than a less beautiful natural gemstone.
No test can be worth as much as the word “natural” on the gemmological certificate:
A gemmologist must carry out many different tests to establish if a gemstone is natural or synthetic, one single test is often not enough. If the gemstone does not show inclusions even under high magnification, the gemmologist may need to have it analysed by a main institute using very expensive equipment in order to come to a definitive conclusion.
For this reason many rare gemstone dealers prefer a gemstone with a microscopic inclusion to a totally pure gemstone: that little inclusion is considered the clue and the conclusive evidence of the gemstone being natural.
In a gemmological certificate, it is very important to notice the word near the species and the mineralogical variety: “natural” or “synthetic” can make the difference