Can aquamarine be heat-treated?

Yes, aquamarine is routinely heat-treated, at roughly 400°C to 450°C, to permanently erase those naturally occurring greenish or brownish tints that show up. In the jewellery business, this is basically standard; it boosts the specimen so you get that pure, vibrant blue which everyone really wants.

The way the heat treatment works is by changing the valence state of iron impurities inside the beryl crystal lattice. This shifts the colour profile while avoiding damage to the stone’s structure. In general, it is completely stable, widely accepted, and expected for most commercial aquamarines unless someone clearly certifies it as untreated. Also, the structural change is not noticeable even under microscopic checks, so heat-treated aquamarine is typically valued in much the same way as naturally blue stones with the same hue.