Can rubies be heat-treated?

Yes, most commercial rubies go through heat treatment to boost the vividness of their colour and also dissolve those cloudy inclusions, leading to better clarity. This thermal enhancement is, in fact, an industry-standard permanent practice that is accepted worldwide, without much debate.

By warming rubies to somewhere between 900°C and 1900°C, the process resembles the real geological conditions where the stones first formed. During heating, unwanted purplish or brownish nuances can be reduced, so the red tone comes through more cleanly. Since high-quality, naturally unheated rubies are extremely uncommon, they usually get a major price uplift (often two to three times more) compared with heat-treated stones that look similar, and that means sellers need strict disclosure at the time of sale.