GIA Gemology Guide: Bruise Inclusions in Diamonds

For a GIA student or professional jewelry appraiser, identifying the exact nature of a surface-reaching characteristic is crucial for both clarity grading and assessing the long-term durability of a diamond. A bruise is a specific type of inclusion that requires careful observation, as it represents both surface damage and internal structural compromise.

1. What is a Bruise?

A bruise (often referred to historically as a "percussion mark") is an inclusion that originates on the surface of the diamond and extends slightly inward. It is characterized by surface damage accompanied by tiny, root-like feathers radiating down into the stone.

How do they form? Unlike cavities, which are usually a byproduct of the manufacturing process, bruises are almost exclusively the result of wear and tear or blunt force trauma. They occur when:

The diamond sustains a sharp impact or localized blow against a hard object (like a countertop, another diamond, or a metal edge).
The force of the impact shatters the crystalline structure at the point of contact, creating a small, pulverized area on the surface with tiny stress fractures (feathers) propagating downward.

Note: Bruises are most commonly found on the facet junctions (the edges where facets meet) or on the crown facets, as these areas are most exposed to daily wear.

2. How to Plot a Bruise (GIA Standards)

Although a bruise involves surface trauma, the GIA treats it strictly as an internal characteristic (inclusion) because of the internal fracturing (feathers) that extend into the diamond. Therefore, it is plotted using only red ink.

Red: Indicates internal characteristics (inclusions).

Plotting Steps:

Locate the Feature: Examine the diamond closely under 10x magnification, paying special attention to the crown facets and facet junctions. Look for what appears to be a small, white, cottony, or fuzzy patch. Use darkfield illumination to make the internal feathers stand out.
Plot the Symbol (Red X): Using a fine-tipped red pen, draw a small "X" exactly where the bruise is located on the plotting diagram.
No Green Ink: Even though the impact originates on the surface, do not use green ink. Per GIA standards, a bruise is denoted solely by the red "X".
Key to Symbols: Ensure "Bruise" is listed in the key in the appropriate order based on its impact on the clarity grade, represented by the red X symbol.

3. Bruise vs. Similar Characteristics

It is important to differentiate a bruise from other features that may look similar under magnification:

Bruise vs. Chip: A chip is a shallow break on the surface, usually with a somewhat jagged edge, but it lacks the tiny, root-like internal feathers extending downward. If there are no radiating feathers, it is just a chip (plotted in red or red/green depending on depth and location, rather than an X).
Bruise vs. Nick: A nick is a very minor, localized surface break, often found along the girdle or facet junctions. It is strictly a blemish and has no internal depth or feathers.
Bruise vs. Crystal: A small, included white crystal might vaguely resemble a bruise at a quick glance, but a crystal is entirely enclosed within the stone and will not show surface damage or the characteristic "root" structure of a percussion mark.

4. Evaluation and Appraisal Considerations

When evaluating diamonds, particularly in estate jewelry or rings that have been worn daily for years, bruises are a common find and an important factor in condition reporting.

Impact on Clarity Grade: The effect on the clarity grade depends entirely on the size and number of the bruises. A tiny bruise on a facet junction might keep a stone in the VS or SI range. However, a large, highly visible bruise on the table facet will lower the grade significantly.
Durability Risks: A bruise represents an area where the diamond's atomic lattice has been compromised. The radiating feathers are tiny fractures; a subsequent hard blow exactly on or near the bruise could cause those small fractures to propagate (grow), potentially leading to a larger chip or a significant crack in the stone.
Appraisal Value: For appraisers, noting bruises is vital for documenting the condition of a piece. A heavily bruised diamond indicates rough wear. If the stone needs to be removed from its setting for repair, the jeweler must be warned, as applying pressure near a bruised area could cause further damage. A significant bruise will negatively impact the stone's valuation due to both the clarity downgrade and the inherent durability risk.

Summary for GIA Students

Definition: Surface impact mark with tiny, root-like feathers radiating inward.
Plotting: A single Red X marking the location (No green is used).
Key Factors: Look for them on exposed areas like facet junctions and the crown. Distinguish them from simple chips by verifying the presence of the internal root-like feathers.

What if the bruise doesn't penetrate?

If a diamond sustains a surface impact that does not result in internal, root-like feathers, it is no longer classified as a bruise. Instead, it falls under a different category of external blemish, which would be plotted in green:

Pit: A tiny, isolated opening on the surface (plotted in green).
Abrasion: A series of minute scratches or chipped areas, typically along a facet junction (plotted in green).
Nick: A minor surface indentation usually found along the girdle (plotted in green).

Ultimately, it is the presence of those microscopic internal feathers that upgrades the feature from a surface blemish (green) to an internal inclusion (red).