Non-Standard Methods of Treating Sapphires

In the world of fine jewellery, there are two key components to keep in mind: metal and gemstone. Over the years much investment and research have gone into studying and measuring the value of gemstones in terms of their authenticity, and the quality and reliability of the precious metal. The main driver of this market scenario has been determined by the higher cost involved with gemstones and precious metals, which are integral to the making of fine jewellery. In the purchase of solid gemstones without the stylistic additions of metals designs, shapes etc. The same principle holds. Gemstones are rare, whilst this depends on the type of gemstone (e.g. sapphire, diamond emerald, ruby), and the specific colour, which varies even among gemstones that are traditionally associated with a designated colour (e.g. blue sapphires). The demand for gemstones, particularly high-quality stones that measure up in terms of the 4Cs (a standard used in the diamond industry) that rate a gemstone’s quality in terms of its colour, clarity, cut and carat. In the world of sapphires, this same standard of gemstone measurement in terms of quality also applies to non-carbon-based gemstones. However, when it comes to the making of quality fine jewellery, the supply of sapphires that meet the highest gemstone standards, and which are also available at competitive prices are not abundant. This has led to the rise of one: man-made or synthetic sapphires, and two: treated sapphires. Whilst synthetic sapphires hold their own particular position in the sapphire industry, treated sapphires are a more complex addition to this mix. Primarily due to the various types of sapphires treatments in the market today. Here we will uncover the various ways in which sapphires are treated, to enhance their character, but the methods which are adopted, fall outside the boundaries of what is ethical and acceptable.

Treatment of Sapphires

With the growing demand for gemstones, a number of countries and companies have entered the fray, increasing the growing supply for these gemstones. The need to provide quality offerings, over the years has meant that certain companies have sought hard to meet this demand by trying to offer quality gemstones that meet top industry standards. With top gemstones such as sapphires being the centre of jewellery and gemstone companies fascination. As the market for fine jewellery steadily grew around the world, the demand for high-quality gemstones was not always matched by the availability of quality gemstones that met the criteria of gemstones that meet the standards in terms of colour, clarity and cut. In the real world, whilst the supply of sapphires, despite being limited, is nonetheless strong. With top sapphire producing countries like Thailand, Ceylon (Sri Lanka), Myanmar, and in recent times gem exporting countries like Tanzania leading the way. However when it comes to securing quality sapphires that meet top standards in colour: in terms of its vividity, tone, variety of shades proves a challenge to many. So companies in their attempt to meet market demand for quality sapphires have sought to improve rough-cut gemstones artificially. Which in turn has given rise to the industry of sapphire enhancement, which falls under the heading of sapphire treatment. The pros and cons of sapphire treatment is a vast subject, as it pertains to the various types of sapphire treatment methods out there. The most popular and accepted practice being the treatment of sapphire via heat treatment. This is a point that we have covered in a dedicated page on sapphire heat treatment. Here we will engage certain less well-known, but yet widely practised sapphire treatment methods. Which in practice are recognised for their sapphire enhancing powers, but the nature of their methods raises serious questions in terms of their final effects on the integrity of the sapphire stone.

Cobalt Coating of Sapphires

Cobalt coating or cobalt doping involves the creation of a thin layer on the surface of the stone, the aim of this method of sapphire treatment is to change the colour of the stone. Since colour is arguably the most critical aspect of sapphires, notably blue sapphire which are found in a numerous variety of shades, tones etc. Since sapphires that are most valued in the market are those which match distinct colour tones in the light and darker shades. Jewellers and gem merchants in order to meet these requirements can resort to a variety of ways: either purchase more expensive stones that meet these colour requirements, work within acceptable sapphire enhancement methods, such as sapphire heating. When it comes to cobalt coating, the sapphire stone, as the name implies is coated entirely in the specific element. What is interesting about cobalt coated sapphires is that the basic qualities of the gemstones remain the same: in terms of the stone’s refractive index and specific gravity values. In addition to the lustrous colour that has been artificially enhanced by the addition of the new element, one may be tempted to that this stone is no different from an authentic natural sapphire.

What Makes Cobalt Coating of Sapphires Problematic?

In the sapphire industry, and in the gemstone business in general, a key point is the presence of expert opinion. A key factor when purchasing any gemstone is the presence of a lab certificate, which can be obtained on request. Which among other tests by experts, involves the microscopic examination of the gemstone. In the case of cobalt coated sapphires, the presence of unnatural fissures, that holds an uncanny blue foreign substance is one example. fissures filled with a rich blue substance that stood out strongly against the otherwise near colourless sapphire. This externally introduced colour can be used to enhance the existing weak colour of the stone or to add new colour altogether to a colourless (white sapphire). One of the natural features of sapphires is their pleochroic character: where the object displays different colours, depending on the angle from which it is viewed. Cobalt coating as a gemstone treatment method negates this quality, and further, the very colour that is present in the stone is due to an external element. Since colour in sapphires is the result of small amounts of trace elements that are present in the stone, that enter it in the course of its development, the colour in sapphire is considered a natural element. Cobalt coated sapphires’ colour is an unnatural external addition. 

Titanium Diffusion

Now onto a more complex form of sapphire treatment. Titanium diffusion is a practice that goes back decades. In fact, the practice is registered under a U.S patent, that was filed in 1975, titled: Altering the Appearance of Corundum Crystals. As the name implies the method is aimed at changing the external character of a gemstone, via a process that involves the artificial introduction of titanium (and iron) agents that can reproduce the natural effects of trace titanium and iron present within naturally coloured blue sapphires. In this case, produce the lustrous blue colour artificially. Since the blue hue in traditional blue sapphires emerges as a result of the interaction of iron and titanium ions with aluminium ions present in the gemstones; the titanium diffusion seeks to artificially bring about these effects. However, this process only changes the colour of the sapphire at the surface level, as the mechanism involves the heating of the corundum crystal, causing the lattice of stone to expand, which then allows heated titanium ions to locate to those areas near the surface. The key point to consider is that in titanium diffused sapphires, additional or new amounts of elements such as titanium, iron and even aluminium oxides are added into the gemstone, which is then subject to heating. The heating stage is the next key step in the titanium diffusion process. The heat level and the number of times it is carried out will vary, but the principle remains the same. Titanium diffusion is a method of artificially improving the colour of the sapphire stone, or introducing new colour via external means to a colourless sapphire.

The Problem with Titanium Diffusion of Sapphires

Titanium diffusion which falls under the heading of corundum surface diffusion is a method that is used to enhance or add colour to sapphire stone by way of introducing external elements and then subjecting them to varying levels of heat, for different time durations; with some of these heating, times can stretching for days. Certain types of targeted sapphire titanium diffusion techniques are even used to create artificial star sapphire effects. The advantage of this process aside, the main problem lies in the artificiality of the method. Akin to the cobalt coating of sapphires, titanium diffused sapphires, get all or most of their colour externally. So the colour is not natural to the gemstone. Unlike conventional heat treatments which seek to improve the colour potential inherent in the gemstone, this method seeks to alter the mineral character of the stone artificially. Which makes titanium diffused stones, essentially unauthentic. Further, the changes introduced by titanium diffusion remains at the surface level, for the level of penetration of the diffusion whilst varied in practice, nonetheless is meant as a more cosmetic improvement, with the actual colour character of the gemstone (i.e. poor or no colour) being visible upon deeper scrutiny. And there have been cases that repeated polishing of titanium diffused sapphires causing the colour of the stone to fade. 

Beryllium Lattice Diffusion

The next candidate on the list of unethical sapphire treatments is the Beryllium lattice diffusion method. Which focuses on high penetration, high heat treatments that aim to produce deep changes to the character of the stone. Unlike titanium diffusions where changes to the colour remain at the surface level of the gemstone, the very high heat that is used to enhance sapphires with the addition of the key element beryllium, indicates deeper changes to the character of the gemstone. Beryllium lattice diffusion is a more invasive form of sapphire treatment that was introduced in the 2001-2002 period and is a predominant practice in sapphire producing countries like Thailand. Beryllium is a chemical element in the table (Be) that is silvery-white in colour, with low density. When beryllium is added to the gemstone via a process of diffusion at high temperatures, that causes deeper penetration into the latticework of the gemstone, and alters the chemical character of the stone, causing changes to the atomic structure of the sapphire. Leading to changes in its colour, which could be a darker, lighter tone or a different kind of hue.

Problems with Beryllium Diffused Sapphires

Beryllium diffused sapphire like titanium diffused stones, get all or most of their final colour owing to the addition of external elements. So the colour in the gemstone is not authentic. Further, beryllium diffusion insoles the addition of a foreign element that is not usually found in natural sapphires, unlike iron or titanium. Further, the high heat method causes changes to the structure of the stone, and some of these changes are undesirable from the stand other measures of sapphire quality. For in addition to causing colour zoning (where the hue levels are not uniformly present throughout the stone), beryllium heat treatment also causes other types of changes, such as altering the crystal of the stone and even introducing glass residues. Beryllium treatment can be considered a desperate attempt to modify the character of the stone to make it more marketable, in the absence of stones that carry genuine colour, and quality in other areas of value. Identifying the presence of beryllium is not as simple as in other types of treated gemstones, and identifying their involvement often requires the use of advanced technologies like SIMS (secondary ion mass spectrometry: which measures the trace-element concentrations in gems down to very small percentages. Beryllium lattice diffused gemstones upon inspection reveal deeper changes to the gemstone at the atomic and structural levels, which raises the question: are beryllium lattice diffused sapphires be considered as authentic natural sapphires stones?