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diamond Inclusion

Laser Drill-hole

GIA Laser Drilling Image
Heavily lasered diamond
clear laser drill holes
Laser Drill holes multiple

GIA GEM 230 STUDY GUIDE: LASER DRILL-HOLE (ld)

Master Instructor's Directive: Master the exact definition, visual presentation under standard 10x magnification, plotting rules, and differential diagnosis of this characteristic.

1. OFFICIAL GIA DEFINITION

  • Characteristic Type: Inclusion/Blemish (Combination)
  • Abbreviation: ld
  • Definition: A tiny, surface-reaching tube produced by a laser beam.
  • Purpose/Origin: Created to provide access to a dark internal inclusion, which is then typically vaporized by the laser or bleached using acid introduced through the resulting tube.

2. VISUAL CHARACTERISTICS (10x Magnification)

When examining a diamond in the face-up or profile position using darkfield illumination, a laser drill-hole presents specific morphological traits:

  • Profile/Path: A remarkably straight, narrow, and uniform tube.
  • Surface Connection: It is, by definition, surface-reaching. You will observe a distinct, perfectly circular opening at the facet surface. 
  • Texture/Appearance: The walls of the tube often display a distinct, microscopic rippled or "threaded" appearance (resembling a screw) due to the pulsing nature of the laser beam during its creation.
  • Termination: The tube usually terminates at the site of a remnant inclusion or an empty space where an inclusion was successfully bleached/vaporized.

3. STRICT PLOTTING PROTOCOLS

Failure to plot correctly will result in point deductions on your final lab exam.

  • Color: Red and Green. (Because a laser drill-hole originates on the surface and extends into the interior of the diamond, it requires both colors). 
  • Symbol: A green circle representing the surface opening, with a straight red line extending inward to indicate the depth and direction of the drill tube.
  • Placement: * Must be plotted accurately on the facet where the surface opening occurs.
    • The depth and angle of the line on the plot must correspond directly to the physical angle and depth of the drill hole inside the stone as viewed face-up.
    • If viewing from the pavilion, it must be plotted on the pavilion diagram.
  • Key to Symbols: Must be listed under "Inclusions" as "Laser Drill-Hole" in the exact order of its impact on the clarity grade.

4. CLARITY GRADING IMPLICATIONS

  • A laser drill-hole is an artificial enhancement, but for GIA grading purposes, it is treated as an inclusion and factored into the final clarity grade.
  • The presence of a laser drill-hole dictates that the diamond cannot receive a clarity grade of Flawless (FL) or Internally Flawless (IF).
  • The overall clarity grade depends on the visibility, size, number, and location of the drill hole(s), as well as any other clarity characteristics present.

5. DIFFERENTIAL DIAGNOSIS: DIFFERENTIATING SIMILAR INCLUSIONS

Do not confuse a laser drill-hole with natural inclusions or other treatments. You must use magnification, darkfield illumination, and varying angles of observation to differentiate them based on the following criteria:

A. Laser Drill-Hole (ld) vs. Needle (nd)

  • Needle: A natural, long, thin crystal. It is completely enclosed within the diamond. It usually has tapered or pointed ends and lacks the perfectly circular surface opening of a laser drill-hole.
  • Differentiator: Check the surface with reflected light. If there is no surface opening, it is not a standard laser drill-hole. A drill-hole has uniform width; a needle may taper.

B. Laser Drill-Hole (ld) vs. Etch Channel (ec)

  • Etch Channel: A natural, hollow tube caused by chemical erosion during the diamond's journey to the earth's surface.
  • Differentiator: Etch channels are rarely perfectly straight. They typically exhibit angular, jagged, or stepped walls (often following the diamond's octahedral growth structure), whereas a laser drill-hole is a perfectly straight tube with a "threaded" or rippled cylindrical wall. Etch channel surface openings are often square, rectangular, or irregular, unlike the perfect circle of a laser drill-hole.

C. Laser Drill-Hole (ld) vs. Internal Laser Drilling (ild)

  • Internal Laser Drilling (ild): A newer treatment where a laser is focused entirely inside the diamond to create a localized expansion (a feather) that reaches the surface, allowing acid to seep in.
  • Differentiator: ILD does not leave an open tube (drill-hole). It leaves a planar, surface-reaching fracture (plotted as a feather or a specific zigzag symbol depending on GIA updates, always in red) and often a dark, burnt remnant where the laser was focused. If there is no distinct tube, it is not a standard laser drill-hole (ld).

D. Laser Drill-Hole (ld) vs. Pinpoint String

  • Pinpoint String: A linear formation of tiny, individual crystals (pinpoints).
  • Differentiator: Under high magnification, a string of pinpoints resolves into discrete, separate dots with space between them. A laser drill-hole is a continuous, solid, linear tube.
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