Heated or Unheated Sapphire?

Sapphire heating is an extremely common process, carried out in a high-temperature kiln (up to approximately 1,800 °C) or by traditional means. It was already practised in antiquity: the merchants of Ceylon were heating their stones long before the age of gemological laboratories.

The aim is to improve what nature left unfinished: inclusions, insufficient intensity or uneven colour. Many blue sapphires are naturally too light or too dark to be set in jewellery — heating gives them the saturation they lack. And this applies to the various colours of sapphire: violet sapphire, yellow and pink are frequently heated as well.

At equivalent quality, an unheated sapphire commands a premium of approximately 30 to 50 % over its heated counterpart — it is rarer, and the market rewards that rarity. Some stones combine several rarities: unheated Burmese sapphire, with its remarkable clarity and brilliance, or unheated Ceylon sapphire, prized for its quality and diversity of hues, can attract premiums far in excess of that.

However, the price of a sapphire does not depend on heating alone: colour, clarity, weight and origin all carry greater weight. A high-quality heated sapphire can very well be worth more than a less exceptional unheated stone.

"Treatment" is a catch-all term that covers very different realities. Simple heating is accepted everywhere; other processes alter the very nature of the stone. This is THE distinction to understand before you buy:

In every case, the rule is the same: any treatment must be stated on the gemmological certificate — as required by French law. Declared, a treatment is not a deception; concealed, it is. It is worth noting that among the major precious stones, the emerald is an exception — it is not heated (its traditional treatments involve oiling, which is a separate matter).

With the naked eye, it is impossible — even for a professional. Only a gemmological laboratory, by analysing the stone's internal inclusions under a microscope, can distinguish a heated sapphire from an unheated one: heat subtly alters certain inclusions (rutile "silk", in particular), and these signs do not deceive a trained eye.

Colour, on the other hand, can bear witness to the journey: take a pink sapphire that leaned towards brown before treatment — after heating, the difference is spectacular. That is precisely the point of the process… and the reason why stating it on the certificate is essential. To go further on authentication, see our guide to recognising a sapphire.

Buying an unheated sapphire has real advantages — provided the stone is naturally beautiful, of course. Those who prize authenticity prefer a gem untouched by human intervention; collectors seek rarity and a value that holds better over time. But an unheated sapphire ring may require a long search to find THE stone.

For rings and jewellery, many turn to heated sapphires, for their price or simply because they offer far greater choice of shapes, sizes and colours. And there is no compromise involved: the same hardness of 9/10, the same brilliance, the same jewellery care — heating changes nothing about wearing your ring day to day.

To see how a stone looks once set, browse our sapphire engagement rings: every model specifies whether the stone is heated or not, supported by a certificate — and our atelier can set the stone of your choice in a bespoke ring.