How does heat treatment affect ruby value?

Heat treatment can really cut a ruby’s value way down compared with a stone that never got heated, because heating is an everyday, industry-accepted routine that people use to push the colour further and help dissolve inclusions in lower-grade rough.

Even though heat treatment is fully stable and normal for jewellery-grade stones, an unheated ruby with top visual quality is, in practice, an almost wild rarity from nature. Because of that, a certified unheated ruby may bring a huge price lift, like 50% up to more than 300%, versus a ruby that looks the same but has received standard thermal enhancement.