Are heated sapphires considered natural?

Heated sapphires are completely natural stones that have been put under high temperatures so their colour and clarity are permanently enhanced, yes. The heat treatment, as it is used in the trade, is a widely accepted traditional industry standard, and estimates often say around 90% of sapphires sold are treated this way.

When they are heated, it mirrors the geothermal conditions the stone would have met if it stayed longer in the earth. The process can melt tiny inclusions to boost transparency, and it can also make the tone deeper or sometimes lighter, depending on the original material. Since these sapphires are extracted from the earth and only changed by heat, with no added chemicals or dyes, they are considered a natural gemstone both in legal terms and in scientific classification.