Clarity enhancement is filling surface-reaching fissures with a filler such as oil, resin, wax or glass, so they show less.
In more detail
It is most common in emerald. Organic fillers can dry out or deteriorate, and a jeweler can remove or refill them. So labs state the condition only at the time of examination.
On a grading report
Fissure filling, or indications of clarity enhancement/modification, with the amount: minor (F1), moderate (F2) or significant (F3).
Related terms
- Emerald oiling: Emerald oiling is filling an emerald's fissures with a colorless oil to make them less visible.
- Resin filling: Resin filling is filling a gem's fissures or cavities with a resin, often one that hardens, to hide them.
- 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.
- Enhancement degree: The enhancement degree is the amount of filler a lab finds in a gem's fissures: minor, moderate or significant.
- Fissure: A fissure is a crack in a gem, often open to the surface. Labs use the word for the cracks that fillers can enter.