What is a Natural Sapphire?

Natural, Round Pink Sapphire Gemstone from Tanzania

All of us who love gemstones want to own natural stones. Though high-quality synthetics exist for many gems such as sapphire and ruby, interest in the synthetics is low, despite the fact that synthetic corundum is chemically identical to natural ruby and sapphire.

Synthetic sapphire produced by the flame fusion process is made up of crystals of aluminum oxide, just like natural sapphire. Though many people would refer to these synthetic gems as 'fake', that is not really accurate. Synthetic sapphire is real sapphire. It's just not natural sapphire. This makes it less interesting for most buyers.

What about the case of sapphire that forms naturally in the ground, but is then later enhanced by humans using techniques common in the gem trade? Are these sapphires natural? Many gem dealers and jewelers would say yes. Others would disagree and contend that only an untreated sapphire is truly 'natural'. Yet others would say that certain treatments are acceptable, but others are not.

So where do we draw the line? Here is the opinion of one dealer who trades high value sapphire:

If extreme heating of a sapphire is acceptable to you, you have
entered a slippery slope. If humans have a hand in creating the
beauty through heating and processing, why not accept the
addition of diffusion and chemical treatment to enhance the color
of a stone? This would make it even more beautiful.

If you are willing to accept something that is not rare just because
it is beautiful, you are better off going back and just accepting
something entirely fake, it will save you a lot of money.

Let's see if we can make sense of this recommendation. First the writer argues that "extreme heating" is not acceptable, then he goes on to suggest that a gem is not natural "if humans have a hand in creating the beauty through heating and processing". The writer is worried that there is a "slippery slope" that we'll slide down if we accept any kind of treatment at all. It seems to be a good point - if you accept one kind of treatment, why reject another?

The argument is a good one except for the fact that we must accept some enhancement performed by the human hand. After all, buyers expect that sapphire will be cut and polished by skilled lapidaries. Natural sapphire in rough form is not very attractive. Artful cutting and polishing brings out the color and brilliance of the natural mineral.

Should we say then that any processing of the raw material is acceptable if it simply brings out the properties of the natural gemstone? That would allow heat treatment, since applying heat to sapphire changes the color and/or clarity because of the chemical composition of the gemstone. Indeed it is often argued that heat treatment is similar to a process that occurs naturally in the earth when the sapphire is formed as a result of heat and pressure.

However, many in the gem industry who accept this position would draw the line when it comes to a treatment known as "lattice diffusion". This is a form of heat treatment that involves the addition of chemicals such as titanium and iron that penetrate the gem material and change the color. Unlike heat, it is argued, this is not a natural process because chemical elements are being introduced into the gem.

But as the well-known corundum expert, Richard Hughes, has argued, "ordinary heating diffuses aluminum vacancies and hydrogen in and out; the surface diffusion process works in the same way, but with heavier elements (Ti, Fe, etc.)". Once any kind of treatment is introduced, complex chemical reactions are created in the gem material.

We can fairly use the term 'natural' to refer to gemstones that are mined from the earth, to distinguish them from gemstones that are created in the lab. But once human invention begins to enhance the gem material to maximize its beauty, it becomes very difficult indeed to say where 'natural' ends and 'artificial' begins.

The most important thing for the buyer is to understand the different enhancements that are used on gemstones, and understand how these affect price. Since each new kind of gem treatment is a way of enhancing previously unsaleable material, it is constantly expanding (or at least maintaining) the supply of scarce gemstones in the market. Without these treatments the supply of many gemstones would be so scarce that this article would probably be more about synthetics rather than 'natural' gemstones.