Residues in healed fissures are remains of the heating process, often glassy. They stay in fissures that healed while a corundum was heated.
In more detail
LMHC labs rate the amount as minor, moderate or significant. The residue ranges from fine 'bubbles' to thick films. Glass-filled cavities can also be present. Lead-glass filling is a different treatment, with its own wording.
On a grading report
Indications of heating, with residues rated FAH 1 (minor), FAH 2 (moderate) or FAH 3 (significant). Filled cavities get their own code, such as FAH C3.
Related terms
- Indications of heating: 'Indications of heating' (H) is the standard LMHC lab wording for a corundum that shows signs of heat treatment. The heating changed its color or transparency.
- Heat treatment: Heat treatment is controlled heating of a gem to change its color or clarity.
- Fingerprint: A fingerprint is a pattern of tiny fluid or glassy drops left where a crack inside the crystal healed. It often looks like a human fingerprint.
- Lead-glass filling: Lead-glass filling is a treatment that fills fissures and cavities in corundum, mostly ruby, with high-lead glass to hide them.