Knot A white or transparent diamond crystal that extends to the surface after fashioning.

GEM 230 Diamond Grading Practicum

Clarity Characteristics Study Guide: The Knot

Characteristic: Knot

Standard Abbreviation: K

Category: Inclusion (with surface manifestation)

1. Official GIA Laboratory Definition

A Knot is defined strictly as an included diamond crystal that extends to the surface of a diamond after fashioning.

Instructor's Note: Do not confuse this with a standard crystal (Xtl), which is entirely enclosed within the host diamond. If it breaks the surface, it is a knot. Period.

2. Microscopic Identification (10x Magnification)

When examining a stone during your GEM 230 practical, you must rely on definitive visual evidence, not guesswork. A knot can be identified by the following laboratory characteristics:

Surface Boundary: You will see a distinct, transparent boundary line on a facet where the included crystal breaches the surface.
Differential Hardness (Relief): Because the included diamond crystal almost always possesses a different crystallographic orientation than the host diamond, it reacts differently to the polishing wheel. The knot will often stand slightly in relief (raised) above the host facet.
Drag Lines: The difference in directional hardness frequently causes the polisher's wheel to "drag" over the knot, leaving microscopic comet-tail trails or drag lines extending from the knot across the facet.
Interference Colors: Under darkfield illumination, you may observe strain or a slight iridescent disruption around the boundary of the knot.

3. GIA Plotting Protocol: The Red and Green Mandate

Plotting requires absolute accuracy. Because a knot exists both inside the diamond and on its surface, it is one of the few characteristics that mandates the use of both red and green ink.

Red Ink represents internal characteristics (Inclusions).
Green Ink represents external characteristics (Blemishes).

How to Plot a Knot (K):

The Surface Boundary (Green): First, map the exact geometric shape of the knot where it breaks the surface of the facet. Draw this outline entirely in GREEN. This indicates the surface manifestation.
The Internal Crystal (Red): Second, map the internal body of the crystal. Draw the exact same shape in RED, placed immediately inside the green outline.
Result: The final plot must show a red outline tightly enclosed by a green outline, matching the exact shape, scale, and location of the knot on the facet diagram.
Key to Symbols: You must list the abbreviation "K" in the Key to Symbols in the correct hierarchical order (based on its impact on the clarity grade).

Failure to use both red and green, or drawing generic circles instead of the characteristic's actual shape, will result in deducted points on your plotting exam.

4. Impact on Grading

As a GEM 230 student, you must understand how this characteristic affects the overall report:

Clarity: A knot is a grade-setting inclusion. Depending on its size, location, and relief, it typically places a diamond in the SI (Slightly Included) to I (Included) categories.
Polish: Because knots often cause surface drag lines and raised relief, the presence of a knot will frequently limit the diamond's Polish grade.
Durability: A large knot near the girdle or a vulnerable facet junction poses a structural risk and may act as a locus for future cleavage.

5. Instructor's Final Warning for the Exam

Do not confuse a Knot (K) with an Indented Natural (IndN) or a Cavity (Cav).

An Indented Natural is a portion of the original rough skin dipping below the polished surface (plotted in red and green, but look for trigon growth marks).
A Cavity is an angular void left when an inclusion falls out during polishing (plotted in red and green, but it is empty space).
A Knot is a solid, transparent diamond crystal that is still physically present and flush (or slightly raised) at the surface.

Study the crystallographic orientations and master your darkfield lighting techniques. I expect perfect plotting on your next assessment.