Professional Jeweler Archive: Devilishly Small

June 2004


Devilishly Small

EGL USA researcher Nicholas Del Re, studies a microscopic new twist in lasering diamonds and offers identification clues

Think about the width of the average human hair, about 100 microns. Now divide that by 20 and you’ll have the approximate width of the laser beam, about 5 microns, in new technology used in diamond treatment.

Nicholas Del Re, an EGL USA researcher based in New York City, has been studying the newest developments in diamond laser technology. He says the trend is toward smaller and less noticeable intrusions into a diamond. “It’s beginning to approach nanotechnology and microfabrication, similar to uses found in other industries,” he says.

Should the jewelry industry care? It should, he says, because the inclusions created in the process often have a very “natural” look, hardly noticeable unless you look for them specifically. Further, drill holes are minuscule, often requiring magnification of 200X to 1,000X (conventional gemological microscopes are 40X to 120X). If you miss these hard-to-see signs of laser treatment, the door is open to deception and an erosion of consumer confidence. Del Re says EGL USA sees the new laser technique in one of every 30 diamonds it examines.

The goal of the new technology is the same as with conventional laser drilling: to reach internal inclusions and eliminate unsightly black piqués (dark crystals) through subsequent acid boiling. “That’s an area that’s known and understood. We are now entering an area at the molecular level that we don’t yet understand fully and where future developments bear watching closely.”

Micro KM

The laser treatment has been dubbed micro KM. The KM stands for kiduah mayuhad, a Hebrew expression meaning special drill. The technology and subsequent applications originated in Israel. In effect, the lasers are used like conventional, though microscopic, drilling machines, including techniques such as operator-managed laser strength and pulsing. “Operators can nudge a laser device at will, creating a natural-looking diversion in the stone,” he says. “Various operators have their own signature techniques, and no one divulges what they are doing.

“For the customer who has a diamond with a high number of inclusions, getting rid of just some of them might raise the price if sold without disclosure.”

What to Look for

Del Re, who has studied hundreds of such stones, has seen a quality progression in micro KM. He divides them into standard KM, newer KM and micro KM. Few features are visible using conventional microscopy. His observations:

  • Standard KM – Reseachers who have studied lots of diamonds notice something doesn’t look “natural” about the internal characteristics. Sheet-like feathers that are highly white and reflective sometimes break the surface. Near the center of the sheet is the appearance of a dark hair-like squiggle. On the surface, the entrance break is linear and not a hole, as with conventional laser drilling.
  • Newer KM – Isolated and grouped linear drills are irregularly shaped and can be elongated or short and black. Sheet-like features can be seen in KM complexes. Surface-reaching breaks may look linear or like tiny needle openings.
  • Micro KM – Isolated and grouped linear drills are irregularly shaped and can be elongated or short and black. KM complexes have unusual scallop-looking feathers near the drill holes. There is no visible connection between the drill hole and the surface at conventional gemological magnifications. Under very high magnification, filament-like channels can be seen from the KM complex to the surface. A microscopic break exists at the surface.
  • EGL USA, New York City; (212) 730-7380.

– by Robert Weldon, G.G.


At 1000X you see an opening (left) that extends into the diamond along a squiggly path. At lower magnification the squiggly line appears straight.
A cluster of KM drill holes near the diamond’s girdle.
This enlarged illustration shows the differences among human hair, which is 100 microns wide (A), the smallest diameter visible to the naked eye, 50 microns (B) and a micro KM drill hole, 5 microns (C).
Micro KM drill holes can appear to have scalloped patterns.
The surface-reaching opening of a micro KM magnified 500X.

Copyright © 2004 by Bond Communications