- Nature of gemstone: This technique is usually applied to diamonds.
- Materials used: A strong and thin laser beam for the drilling process, a vacuum furnace for cleaning & lead glass for final filling.
- Possible effects: Generally used to remove coloured impurities in diamonds and thereby improve the clarity.
- Under magnification a difference in the lustre of lead glass and the diamond on the surface is noticeable.
- Colour flashes along the drill hole is seen on rotating the stones at varying angles namely yellow, orange and blue colour flashes.
- Discoloration along the drill hole
- The drill hole maybe a single channel drill hole or a series of laser drill holes in a single plane giving a fan like pattern and a surface break which appears as a thin rectangular depression.
KM treatment: Recently a newer technique has been introduced in 2000 A.D. known as KM treatment. This treatment is used on black inclusions accompanied by internal fractures. One or more pulsed laser beams are focused on the inclusion itself with the resulting heat creating an internal fracture. The point of focus of beam is then moved towards the closest surface of diamond at the same time creating a continuous fracture from the inclusion to the surface. After this, diamond is boiled in strong acid with pressure, to allow the solution to bleach out the inclusion. Identification of treatment is almost impossible.