Glossary
Heating with residues (TE1–TE5)
When ruby and sapphire are heated, additives can melt and close fissures, leaving glassy residues. Laboratories grade their amount: TE for heating without residues, TE1–TE2 for minor, TE3–TE4 for moderate and TE5 for significant residues. C1 to C3 denote residues in cavities. The higher the grade, the stronger the intervention and, as a rule, the lower the value.
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Updated 2026-10-04