Gemstone treatment
Heat Treatment, Corundum
Under 10x loupe or microscope: partially dissolved rutile silk, broken needles, heat-altered crystals, discoid stress fractures around inclusions, or blue color concentrated along healed fractures in some sapphires.
01
What to look for
Under 10x loupe or microscope: partially dissolved rutile silk, broken needles, heat-altered crystals, discoid stress fractures around inclusions, or blue color concentrated along healed fractures in some sapphires.
02
What it means
Heat is the most common corundum treatment. It can improve color and clarity, but unheated ruby and sapphire with fine color command a premium.
03
Expert move
Compare silk across the whole stone. Intact silk supports unheated status, while melted or interrupted silk is one of the strongest heat clues.