No heat
A laboratory finding that a ruby or sapphire shows no indications of heat treatment.
Most rubies and sapphires are heated to improve their colour and clarity. An unheated stone of fine colour is rarer and worth considerably more, especially with a report of origin such as Burma, Kashmir or Ceylon.
What to look for
Ask for the report and check its date and laboratory; the leading ones include GIA, AGL, SSEF and Gübelin.
Related terms