Diamond Inclusion Study Guide: Indented Natural (IndN)

GIA Definition

An indented natural (abbreviated IndN on plotting diagrams, though the full name is always spoken) is a portion of the original rough diamond crystal surface, or "skin," which dips below the polished surface of the finished faceted stone.

Essential Characteristics

Location: By definition, an indented natural must intersect the surface of the diamond. It cannot be entirely internal. They are most commonly found at the girdle, often spanning across the upper and lower girdle facets, but can technically occur anywhere a depression in the original rough was not entirely removed during the cutting process (e.g., culet, pavilion main).
Surface Texture: The surface of an indented natural often (but not always) exhibits characteristics of the original rough crystal. This may include:
- Trigons (triangular growth marks, common on octahedral faces).
- Parallel grooves or striations.
- A generally frosted, unpolished, or "gletz-like" appearance compared to the surrounding polished facets.
Depth: It is a cavity; it has measurable depth extending into the body of the polished diamond. This is the key distinction between a simple natural and an indented natural.

Plotting Protocols (GIA GEM 230 Standards)

Accuracy in plotting is paramount. An indented natural requires specific notation because it is a characteristic that is both external (intersecting the surface) and internal (extending into the stone).

Symbol and Color

Symbol: An indented natural is plotted using the specific shape of the inclusion as seen under magnification.
Color: Because it penetrates the surface and enters the stone, it is plotted in RED (for the internal portion/outline) and GREEN (for the surface-reaching aspect).
Execution: You must draw the exact outline of the indented natural in RED. Then, trace only the portion of the outline that intersects the polished surface (usually the girdle edge or a facet junction) in GREEN. The green line must perfectly trace over the red line at the point of surface intersection.

Key Plotting Rules

Do Not Over-Plot: Plot the size and shape accurately relative to the facet it occupies. Do not exaggerate its size.
Facet Junctions: If the indented natural crosses a facet junction (e.g., from an upper girdle facet across the girdle to a lower girdle facet), the plot must accurately reflect this crossing on both the crown and pavilion diagrams if visible from both views.
Nature of the Surface: While the texture (trigons, etc.) helps you identify it as a natural, you do not plot those individual textures. You only plot the outline of the cavity.
Comments Section: If the indented natural is significant, it may be noted in the "Comments" section of a full GIA Diamond Grading Report, though its primary documentation is the plot itself.

Differentiating Indented Naturals from Similar Characteristics

This is a critical area for the GEM 230 exam. You must be able to distinguish an IndN from other surface-reaching or cavity-like inclusions.

Indented Natural (IndN) vs. Natural (N)

Natural: A portion of the original rough that remains on the surface but does not dip below the polished surface. It is flat or follows the contour of the girdle. Plotted entirely in GREEN.
Indented Natural: Dips below the surface, creating a cavity. Plotted in RED (outline) with a GREEN line tracing the surface intersection.
Instructor Tip: Run a scribe or probe carefully over the area. If it dips, it's an indented natural. If it's flush, it's a natural.

Indented Natural (IndN) vs. Cavity (Cav)

Cavity: An angular, deep opening on the surface, usually caused by a cleavage plane or an inclusion that was dislodged during polishing.
Indented Natural: While also a depression, it is specifically a remnant of the original rough surface. The presence of crystal growth marks (trigons, parallel grooves) or a frosted texture strongly indicates an indented natural. If the depression appears to have been fractured or broken away, it is likely a cavity.
Instructor Tip: The etiology is the key. Was it left by the cutter (IndN), or did material fall out (Cav)? Both are plotted Red/Green, so accurate identification is crucial for the "Key to Symbols."

Indented Natural (IndN) vs. Chip (Ch)

Chip: A shallow, conchoidal (shell-like) fracture on the surface, typically at a facet junction, culet, or girdle edge.
Indented Natural: Will not have a conchoidal fracture surface. It will have the texture of rough diamond.
Instructor Tip: Chips are post-cutting damage (or cutting accidents). Indented naturals are remnants of the rough.

Exam Focus Points (What to Review)

Red/Green Plotting Rule: Memorize that indented naturals require both red (outline) and green (surface intersection). Failure to use both colors is a common error.
Identification: Practice recognizing the difference between the rough texture of an IndN and the fractured surface of a cavity or chip under 10x magnification.
Plotting Accuracy: Ensure your red outline accurately reflects the shape and size of the inclusion, and the green line is strictly limited to the surface intersection.