The original laser drill holes were much more noticeable than today’s modern drill holes. The old style, going back to about 1970, left a much larger entrance into the surface of the diamond tapering down until it reached the point of destination. Many times the entrance was burned and then had to be polished, which left trailing lines on the surface. Today’s LDH is much finer, perhaps the width of a human hair, with a consistent diameter along its length.
Some natural inclusions are mistaken for LDHs; these could include needle-like crystals and etch features. Etch features are highly unusual and can easily be mistaken for LDHs. They can vary in length and usually form straight lines or step-like patterns. They are hollow and when they break the surface of a diamond, their hexagonal or rectangular cross-sections are apparent. Etch features are easiest to pick out by their angular patterns, in contrast to the straight or slightly bent direction of an LDH (bent by refraction).
Sometimes laser drilling doesn’t work out as planned when the target is missed, potentially creating multiple drill lines, making the stone worse off than before. Not all stones are candidates for drilling. The shop performing the task will be more than happy to give you their best advice on your particular problem stone.
Laser drilling is generally performed in the SI2 to imperfect categories to hopefully raise the clarity by at least one grade or then perhaps the beauty and salability of the stone. Many times it’s a trade-off between a dark inclusion or obvious, unnatural-looking drill lines.
The FTC, (Federal Trade Commission), now requires the disclosure of laser drill holes in diamonds. The diamond industry has always considered it a requirement for such disclosure even before the FTC made it so. It is very important to examine all diamonds for this negative characteristic for the purposes of valuation and proper representation for the next buyer. Even in higher clarity diamonds, it is still possible that small, discreet, drill holes are present.