Introduction
Every natural diamond carries traces of its formation — mineral crystals captured during growth, fractures from tectonic stress, or distortions along twin planes where the crystal lattice changed direction. Gemologists call these traces clarity characteristics, and GIA classifies them into distinct types based on what they are, how they formed, and what they look like under 10x magnification.
The clarity grade on a GIA report (see GIA Clarity Scale) tells you the overall severity. But two VS2 diamonds can contain very different characteristics — one might hold a transparent needle barely visible under the loupe, another a dark crystal that required careful positioning to keep the grade. Understanding what each characteristic type is, and what it means for the stone's beauty and durability, gives you the information the grade alone cannot.
This article covers the ten most common clarity characteristics plotted on GIA reports. For each, we explain what it looks like, how it forms, and when it matters.
Inclusions (Internal Characteristics)
Pinpoint
A pinpoint is a very small included crystal, appearing as a tiny dot under 10x magnification. Individually, pinpoints are the most benign of all clarity characteristics — a single pinpoint is often the sole feature that separates a VVS1 from an IF grade.
How it forms. During diamond crystallisation, microscopic mineral particles become trapped within the growing crystal lattice. They are too small to identify mineralogically under standard magnification.
Significance. A few isolated pinpoints have virtually no impact on appearance or durability. They become a grading concern only when they cluster together to form a cloud (see below) or when they are numerous enough to affect the grade collectively. On the GIA plot, pinpoints are marked as small red dots.
Crystal
An included crystal is a mineral trapped inside the diamond during formation. Under magnification, it may appear as a distinct solid shape — sometimes transparent, sometimes dark. Dark crystals (often garnet, chromite, or iron-bearing minerals) are the most visually conspicuous type of inclusion.
How it forms. As the diamond grew within the earth's mantle at temperatures above 900 °C and pressures exceeding 45 kilobars, other minerals in the surrounding rock became enclosed within the expanding crystal. Some are themselves diamond crystals — in which case the inclusion is transparent and difficult to detect.
Significance. Crystals are the most variable clarity characteristic. A small, colourless crystal tucked beneath a bezel facet may be invisible even under magnification. A dark crystal centred under the table of the diamond is the single most grade-impacting inclusion — highly visible and often the determining factor that pushes a stone from VS into SI territory. Position and relief (contrast against the diamond body) matter enormously. On the plot, crystals appear as small red symbols, sometimes with a colour notation.
Needle
A needle is a long, thin included crystal. Under magnification, it appears as a fine line or rod, often white or transparent. Needles are common in diamonds and are typically one of the less consequential inclusion types.
How it forms. Needle-shaped mineral inclusions — frequently rutile — grow along specific crystallographic directions within the diamond as it forms. Their elongated shape reflects the crystal habit of the trapped mineral.
Significance. Short, fine needles are often difficult to detect even under 10x magnification and rarely affect visual appearance. However, a cluster of long needles, or a needle with significant contrast (dark colour), can contribute meaningfully to the grade. In most cases, needles are the kind of inclusion that makes a VS grade a VS grade — present but inconsequential.
Feather
A feather is a fracture within the diamond. The name comes from its feather-like, wispy appearance under magnification, caused by the way light refracts along the fracture surface. Feathers range from tiny hairline cracks to substantial fractures that cross a significant portion of the stone.
How it forms. Internal stresses during crystal growth, tectonic activity in the earth's mantle, or the forces of extraction and cutting can produce fractures within a diamond. Some feathers formed millions of years ago; others were introduced more recently during processing.
Significance. Feathers are the inclusion type most likely to raise durability concerns. A small feather contained within the interior of the stone is a cosmetic characteristic only — it affects the grade but not the diamond's structural integrity. A feather that reaches the surface, particularly at the girdle or near a thin area of the crown, is a different matter. Surface-reaching feathers at the girdle can make that area vulnerable to chipping during setting or from an accidental impact. On the GIA plot, internal feathers are shown in red; surface-reaching feathers appear in green. If you see green feather symbols near the girdle on an SI or I-grade report, ask the seller about durability implications.
Cloud
A cloud is a cluster of pinpoints grouped closely enough that they appear as a hazy or milky area under magnification. Clouds are sometimes so diffuse that individual pinpoints cannot be resolved — the area simply looks foggy.
How it forms. Clouds form when many microscopic mineral particles become trapped in the same growth zone of the diamond. They represent a region where conditions during crystallisation produced concentrated particulate trapping rather than the isolated events that create single pinpoints.
Significance. Small, localised clouds are typically minor grading features. But large clouds that span a significant area of the diamond can reduce transparency, making the stone appear hazy or lifeless even if the clarity grade suggests otherwise. This is one reason why the clarity grade alone is not a reliable predictor of visual performance — an SI1 with a large cloud may look worse than an SI2 with a single dark crystal. When a GIA report lists "clarity grade is based on clouds that are not shown" in the comments section, this indicates a pervasive cloud that the plot cannot represent accurately. Such stones deserve careful visual inspection. See Clarity-Transparency Bridge for more on the relationship between clouds and visible haziness.
Twinning Wisp
A twinning wisp is a complex inclusion that forms along twin planes — boundaries within the crystal where the atomic lattice changed growth direction. Under magnification, twinning wisps appear as irregular, ribbon-like patterns that may include pinpoints, crystals, feathers, and clouds woven together along the distortion plane.
How it forms. During crystallisation, the diamond may experience a shift in growth direction, creating a twin plane — a mirror-like boundary in the crystal structure. Inclusions concentrate along this boundary because the disrupted lattice preferentially traps foreign material.
Significance. Twinning wisps range from subtle, wispy lines to prominent bands visible to the unaided eye. Their visual impact depends on size, extent, and contrast. Because they consist of multiple inclusion types combined, their appearance is unpredictable from the plot alone. Twinning wisps are particularly common in fancy shapes that are cut from twinned crystals, such as hearts and some cushion cuts. When present, inspect the diamond visually — the plot gives position but not visual severity.
Knot
A knot is an included crystal that extends to the polished surface of the diamond. Unlike a fully internal crystal, a knot can sometimes be felt with a fingernail or seen as a raised or textured area on the facet surface.
How it forms. During cutting and polishing, a cutter encounters an included crystal that is positioned too close to the planned surface to be polished away without losing unacceptable weight. The cutter polishes through or over the inclusion, leaving it exposed at the facet surface.
Significance. Knots are relatively uncommon because skilled cutters work to avoid them. When present, they are a concern both cosmetically and structurally. The exposed inclusion creates a weak point at the surface that can collect dirt more readily and, in some cases, may be vulnerable to chipping. Knots are plotted in green (surface-reaching) and typically lower the clarity grade more than an equivalent internal crystal because they violate the polished surface. In the Czech market, a knot visible on the table facet is a legitimate reason to request a replacement stone or a price adjustment.
Cavity
A cavity is an angular opening in the diamond's surface, created when a near-surface inclusion falls out during polishing or when part of a feather breaks away.
How it forms. If a crystal inclusion sits near the surface and lacks sufficient cohesion with the surrounding diamond, the mechanical stress of polishing can dislodge it, leaving a void. Similarly, a feather reaching the surface may lose material along the fracture during cutting, producing a shallow depression.
Significance. Cavities are surface features that tend to collect dirt and oil, which can make them more visible over time even if they are initially subtle. A cavity on the table or crown is more concerning than one near the girdle, both visually and for cleaning. Cavities are plotted in green and typically have a moderate to significant impact on the clarity grade depending on size and position.
Bruise
A bruise is a small area of impact damage on a facet surface, accompanied by root-like feathers that radiate into the diamond beneath it. Under magnification, the surface shows a conchoidal fracture pattern, and the underlying feathers fan outward from the impact point.
How it forms. A sharp blow or concentrated force strikes the diamond surface — this can occur during mining, cutting, or handling. The impact creates both a surface mark and internal fractures beneath it.
Significance. Bruises are dual-natured: they are both blemishes (the surface mark) and inclusions (the subsurface feathers). Their grade impact depends on the severity of the subsurface damage. A minor bruise near the girdle may have negligible visual impact. A bruise on the table, particularly one with prominent radiating feathers, can be conspicuous and structurally weakening. Bruises cannot be polished away without also removing the underlying feather network.
Surface Characteristics
Indented Natural
An indented natural is a portion of the original rough diamond surface that dips below the level of the polished facet surface. It appears as a small depression, often with a slightly different texture from the polished surroundings — sometimes showing the trigonal growth patterns (trigons) of the original crystal face.
How it forms. Diamond cutters aim to maximise weight retention from the rough crystal. An indented natural occurs when the cutter decides that removing this small area of rough surface would sacrifice too much carat weight. The natural is left intentionally as a trade-off between weight and finish.
Significance. Indented naturals are among the least consequential clarity characteristics. They are typically located near the girdle, where they are hidden by the setting, and have no effect on light performance or durability. On the GIA plot, they are shown in green (surface feature). An indented natural is often what separates a VVS grade from IF — a minor distinction with no practical impact once the stone is mounted.
Reading the Inclusion Plot
The GIA clarity plot on a grading report maps every graded characteristic using standardised symbols:
- Red symbols indicate internal characteristics (inclusions).
- Green symbols indicate surface-reaching or external characteristics (blemishes).
- Symbol type corresponds to the characteristic: dots for pinpoints, lines for needles, branching patterns for feathers, irregular shapes for clouds or twinning wisps.
The plot uses a crown view (top-down) and a pavilion view (bottom-up) to show where characteristics sit in three-dimensional space within the stone. Learning to cross-reference the plot with the grade — and ideally with a photograph or video — is the most reliable way to understand what a specific diamond's clarity means in practice. A quality 10x triplet loupe or microscope lets you see exactly what the plot describes, confirming the grader's observations against what the stone actually shows. See Plot & Comments for a full guide to reading GIA plot diagrams.
Summary
Every diamond's clarity story is written in its characteristics — the specific inclusions and blemishes that a gemologist identifies, maps, and grades. The ten primary types described here differ in origin, appearance, and consequence. Pinpoints and needles are typically benign. Crystals vary enormously depending on colour and position. Feathers demand scrutiny when they reach the surface or the girdle. Clouds can silently compromise transparency in ways the grade alone does not reveal. Understanding these distinctions allows you to evaluate not just a diamond's clarity grade, but what that grade actually means for the stone you are considering — its beauty, its durability, and its value.
All clarity characteristic terminology follows GIA (Gemological Institute of America) standards. For clarity grading criteria, see Clarity Grading Factors.