Feathers, Fractures, Cavities, and Chips
Diamond is exceptionally hard, but hardness does not mean indestructibility. Fractures and surface damage must therefore be described more precisely than with the simple label “crack.” A professional assessment considers the type of characteristic, its 3D position, its relationship to the surface and vulnerable parts of the shape, and the stone’s actual condition.
The most important boundary is:
A clarity grade is not a numerical forecast of future breakage.
Fracture and Feather
A fracture is a general structural break in a diamond. It may be geological, manufacturing-related, or formed later.
A feather is the traditional gemological term for a break in a gemstone that often looks white and feathery. The appearance results from reflections off fracture surfaces and tiny branches of the crack, not necessarily from white material inside it.
A feather may be nearly invisible from one angle and strikingly bright from another. A photograph from a single direction is therefore insufficient to assess its full geometry.
Does It Reach the Surface?
For practical assessment, one of the first questions is its relationship to the external surface.
A fracture may be:
- fully enclosed in the stone;
- very close to the surface;
- connected to one facet;
- open at the girdle;
- connected to a point or the culet;
- open in several places.
Its relationship to the surface may affect the possibility of contamination, treatment, further damage, or a change in appearance after cleaning. The mere fact that a characteristic reaches the surface, however, does not provide a percentage risk of breakage.
[VISUAL 45.1: Enclosed feather, surface-reaching feather, and open fracture—3D cross section through a diamond]
Cleavage Planes and Direction of Breakage
Diamond has pronounced cleavage along {111} planes. This explains why exceptional scratch hardness does not eliminate vulnerability to an impact directed unfavorably relative to the crystal structure.
A visible fracture, however, must not automatically be declared perfect cleavage solely from its appearance. Fracture morphology, crystallographic orientation, and loading history may be more complex.
The full relationship among hardness, toughness, and cleavage was covered in Chapter 2.
Cavity
GIA defines a cavity as an angular opening that may form when part of a feather breaks away or when a surface-reaching crystal falls out or is removed during polishing.
A cavity therefore represents missing material at the surface, not merely an optical line.
Important factors are:
- size;
- depth;
- position;
- sharpness of the edges;
- connection to other fractures;
- ability to retain dirt.
A cavity at the girdle or a point is not the same situation as a very small opening on a protected facet.
Crystal Dropout
If a mineral inclusion is intersected by the surface and falls out during processing, it leaves an opening that may be classified as a cavity. The shape and remnants at the edge can sometimes be used to reconstruct the former presence of a crystal, but this is not always possible.
Documentation before and after polishing or repair is therefore useful.
Chip
A chip is a shallow opening caused by damage to the surface, typically at the girdle, a facet junction, or the culet.
Unlike a cavity, which is often associated with loss of material around a preexisting inclusion or feather, a chip is primarily later mechanical damage to the surface.
It may form during:
- cutting and polishing;
- setting;
- jewelry repair;
- impact during wear;
- contact with another diamond.
Bruise and Bearded Girdle
A bruise is localized impact damage that may have a small point of origin at the surface and tiny feather-like fractures extending into the interior.
A bearded girdle, or bearding, consists of a series of very small feather fractures extending from the girdle into the stone, often as a result of aggressive bruting or other mechanical stress during manufacturing.
Both characteristics may appear subtle until the stone is examined under suitable illumination.
[VISUAL 45.2: Cavity, chip, bruise, and bearded girdle—morphological comparison of surface damage]
Natural and Later Fractures
A fracture may form before kimberlite transport, during ascent, mining, or manufacturing, or many years after the stone has been set in jewelry.
Appearance alone is often insufficient to date the break accurately. An older fracture may be partly mineralized or healed; a newer one may be very clean; surface contamination may make an old fracture look darker.
A microscopic image should therefore not be used without additional context to claim: “this happened in the mine,” “this happened during setting,” or “this is a manufacturing defect.”
Clarity and Durability Are Not the Same
A clarity grade describes the visibility and significance of characteristics according to a grading system. Durability is a mechanical question.
They are related because some fractures can be both readily visible and mechanically significant, but the relationship is not linear.
Two diamonds with the same clarity grade may have entirely different durability profiles. One may have dispersed pinpoints and a crystal inclusion deep within the stone; another may have a surface-reaching feather close to a thin girdle.
The label VS2, SI1, or SI2 therefore cannot be used to calculate a “percentage chance that the stone will break.”
Position Often Matters More Than the Term Alone
For a fracture, consider its relationship to:
- the girdle;
- the point of a pear, marquise, or heart;
- the corners of a princess cut and other angular shapes;
- the culet;
- very thin local areas;
- existing chips and cavities;
- the planned setting.
A small characteristic in a mechanically vulnerable area may warrant more attention than a larger characteristic in a protected zone.
This is still not a universal verdict. A sound recommendation requires examination of the specific stone and setting.
A Two-Dimensional Plot Does Not Show the Full Fracture
A plot shows the characteristic’s approximate position in projections from the crown and pavilion. A fracture is a three-dimensional plane or network.
The plot therefore often cannot reliably reveal:
- exact depth;
- inclination;
- whether it is open to the surface along its entire length;
- whether multiple connected branches exist;
- how close it is to another fracture.
Physical examination under a microscope remains important.
Reflections Can Increase Apparent Size
A single feather may be reflected through the facets and appear to be several cracks. Assessment requires locating the actual fracture plane and separating it from the optical images.
The same problem occurs with the crystal inclusions discussed in Chapter 43.
Secondary Staining and Surface Contamination
An open fracture may acquire dirt or colored material over time. Such secondary staining can alter the characteristic’s relief and color without changing the fracture’s underlying structure.
A professional comparison before and after cleaning must therefore distinguish:
- removed surface contamination;
- a change in the appearance of an open fracture;
- actual removal or extension of material.
[VISUAL 45.3: Crystal with a pressure halo—a solid inclusion, radial fractures, and their reflections]
Pressure Cracks Around an Inclusion
Differences in volume and elastic properties between a mineral inclusion and diamond may create radial or halo fractures. In that case, both the solid inclusion and the surrounding fractures should be documented.
A clarity characteristic that initially appears to be a “large feather” may actually be a combination of a smaller crystal inclusion and surrounding pressure cracks.
Fracture Filling, Cleaning, and the Workshop: Only the Boundary of This Chapter
A surface-reaching fracture may be filled artificially. Such fracture filling changes optical visibility and requires a separate treatment assessment; it is covered in detail in Chapter 59.
Ultrasonic cleaning, steam, heat, lasers, setting prongs, and other workshop situations may be relevant to existing fractures, but no universal rules can be applied safely without examining the stone. The complete cleaning, setting, and repair workflow belongs in Chapters 86–89.
One rule is sufficient here: Before any procedure, identify the surface-reaching and mechanically relevant characteristics.
A Mounted Diamond and a Change in Condition
A setting may conceal part of the girdle, a point, or a surface opening. Assessment of a mounted stone therefore has limitations.
A laboratory report also describes the stone’s condition at the time of examination. A later chip, recut, or extension of an existing fracture may mean that the physical stone is no longer in the same condition as described in the old document.
This is why, before an important purchase, repair, or insurance decision, the stone’s current condition should not be assessed solely against an old report.
Practical Assessment Protocol
- clean the stone and examine it from multiple directions;
- distinguish a feather, cavity, chip, bruise, and bearding;
- determine whether the characteristic reaches the surface;
- assess its 3D position, not just the symbol on the plot;
- separate the actual fracture from facet reflections;
- document its relationship to the girdle, points, and corners;
- record secondary fractures around inclusions;
- check whether fracture filling is suspected;
- photograph and document the existing condition before any procedure;
- make a durability recommendation only for the specific stone and its specific intended use.
[VISUAL 45.4: Plot versus an actual 3D fracture—the same 2D symbol, different depth and surface relationship]
Chapter Summary
- A fracture is a general structural break; feather is a gemological term for a break that often looks feathery.
- A white feather does not automatically mean white filler.
- The relationship to the surface must be assessed separately.
- Diamond cleaves along {111} planes, but not every fracture resembles ideal cleavage.
- A cavity is an opening associated with material loss, often involving a feather or crystal dropout.
- A chip is shallow surface damage, typically at the girdle, a facet junction, or the culet.
- A bruise and bearded girdle are distinct surface-fracture characteristics.
- Microscopic appearance alone often cannot determine when and how a break formed.
- Clarity grade and durability are not the same, and there is no universal percentage risk based on a clarity designation.
- A fracture’s position relative to a girdle, point, corner, or other vulnerable area may be decisive in practical assessment.
- A two-dimensional plot does not show a fracture’s full three-dimensional geometry.
- Fracture filling, cleaning, setting, and recutting require separate professional context and must not be reduced to one generic recommendation.