Fracture-filling with lead glass is done prior to cutting. The rough is first preformed to remove any traces of matrix or other foreign material. For a good description of the treatment process see this report from the AIGS lab in Bangkok:
Some are filled prior, some after, really depends on how the cutter came across the stone and what type of filler. The traditional method of oiling a stone is typically done after cutting. As for if the cutter knows, some are knowledgeable, and some aren't. Higher end treatments, such as ExCel, are typically done after the gemstone is cut. With emeralds, 99% of stones are filled and it is unwise to assume you came across one that isn't unless it comes with a GIA, AGTA, or AGL lab report.
Yes you can fill at any time in the process. What lab had that treatment listed like that?
Most emeralds are treated with cedar oil before they are cut and polished. The cedar oil is thick sticky stuff and it requires heat and pressure to get it penetrate the microscopic cracks in emerald. Usually they do this in hydraulic containers with heat and pressure controls.
If you read the the article I mentioned, the idea of selectively treating certain portions of a gemstone (''at facet junctions'' only) seems far-fetched.
300x240.png)
