Internal Laser Drilling Laser drilling within a diamond that creates a surface-reaching feather, or expands a pre-existing feather around a dark inclusion so that it reaches the surface. The feather then provides access for bleaching to decrease the visibility of the inclusion.

GIA GEM 230 Study Guide: Internal Laser Drilling (KM)

I. Definition and Purpose

Internal Laser Drilling (also known in the trade as Kiduah Meyuhad or KM, meaning "special drill" in Hebrew) is a clarity enhancement treatment.

The Process: A laser is focused directly on a dark internal inclusion (typically graphite/carbon). The intense heat expands the inclusion, creating a microscopic, step-like feather or cleavage that reaches the surface of the diamond.
The Goal: To create a surface-reaching channel without a traditional drill hole, allowing bleaching agents (usually strong acids under pressure) to enter the diamond and dissolve or lighten the dark inclusion.
The Result: The dark inclusion is lightened or removed, but a new feather (fracture) is created. The feather created often looks more "natural" than a traditional laser drill hole.

II. Differentiation: Internal Laser Drilling vs. Laser Drill Hole

It is critical for the GEM 230 exam to strictly differentiate these two treatments.

Feature | Internal Laser Drilling | Laser Drill Hole (LDH)
GIA Definition | Laser-induced feather expanding to the surface to allow bleaching. | A minute, surface-reaching tunnel/tube produced by a laser beam.
Physical Shape | Appears as an irregular cleavage, "worm-hole" channel, or step-like feather. | Appears as a straight, fine, cylindrical tube.
Surface Feature | An irregular break or fracture opening at the surface. | A distinct, round opening/hole at the surface.
GIA Plotting Symbol | NOT PLOTTED as a specific symbol (see plotting rules below). | PLOTTED (Red dot surrounded by a green circle).

III. Strict GIA Plotting Rules for Internal Laser Drilling

For the GEM 230 exam, you must adhere strictly to GIA laboratory reporting standards.

NO SPECIFIC SYMBOL: There is no dedicated symbol for "Internal Laser Drilling" on a GIA plotting diagram.
PLOT THE RESULTING CHARACTERISTIC: You must plot the physical characteristic created by the treatment. Because internal laser drilling creates a fracture, you must plot it using the Feather symbol (drawn in red).
MANDATORY COMMENT: Because the treatment alters the clarity of the stone without leaving a tell-tale drill hole, GIA requires full disclosure. If this treatment is detected, the following statement must be written in the "Comments" section of the grading report:
- "Internal laser drilling is present."
DO NOT USE TRADE TERMS: Never use terms like "KM," "Special Drill," or "Clarity Enhanced" on the plotting diagram or in the standard comments. Strictly use the exact GIA phrase above.

IV. Identification Under Magnification (10x - Microscopy)

When grading, look for these signs to identify internal laser drilling:

An inclusion (often lightened or frosty white) connected to a surface-reaching feather.
The feather may have an unnatural, jagged, or "step-like" appearance.
In transmitted light, you may see convoluted, "wormhole-like" channels within the cleavage, rather than a straight tube.
Lack of a distinct, round drill hole on the facet surface above the inclusion.

V. Exam Prep Checklist (Red Flags)

Did you plot it as a Laser Drill Hole? WRONG. It must be plotted as a feather.
Did you forget the comment? WRONG. "Internal laser drilling is present" is mandatory for disclosure.
Is it a stable treatment? YES. GIA considers laser drilling (both traditional and internal) a permanent, stable treatment and will issue a grading report (unlike fracture filling, which they will not grade).