Heat treatment is a standard step for much of the world's blue sapphire. Rough or cut stones are heated to settle colour and reduce silk so the face-up blue reads cleaner. It is accepted in the trade when disclosed. It is not the same as glass filling or diffusion; we do not sell stones with those treatments.
Unheated sapphire is rarer in strong blues and often carries more visible silk or zoning. Collectors and jewellery buyers pay a premium when the colour is strong without heat. We label unheated stones explicitly on the card and in the description.
Heat treated does not mean low quality. Many fine Ceylon stones are heated to bring out a colour that was already in the crystal. What matters is whether the price reflects the treatment and whether you like how the stone looks in our video.
On this site, treatment appears on the second line of each card and in specifications. If a stone says unheated, we mean no furnace treatment. If it says heat treated, assume conventional heating unless the description states otherwise. Ask on WhatsApp if you need lab paperwork for a specific stone.