Introduction
Clarity describes how clean a diamond is — how free from internal characteristics (inclusions) and surface features (blemishes) when examined under standard magnification. Every natural diamond formed under extreme heat and pressure deep within the earth, and almost every one carries traces of that process: tiny crystals, feathers, clouds, or growth patterns locked inside the stone.
The question is not whether inclusions exist. It is whether they are visible, and under what conditions.
GIA's clarity grading scale provides a standardised answer. It assigns every diamond one of eleven grades based on the size, number, position, nature, and relief of its clarity characteristics as seen under 10x magnification — the industry-standard loupe power. The scale runs from Flawless (no characteristics visible at all under 10x) to Included (characteristics visible to the unaided eye and potentially affecting durability).
Understanding this scale matters because clarity directly influences price — but the relationship between grade and visual appearance is not always proportional. A two-grade drop in clarity can save 20–30 % per carat while producing a diamond that looks identical to the naked eye. This article explains each grade, what it actually means for the stone in your hand, and where informed buyers find value. For an overview of all grading factors, see Diamond in 10 Minutes.
How GIA Grades Clarity
A trained gemologist examines the diamond under 10x magnification using a standard gemological loupe or binocular microscope. The examination is methodical: the grader looks through the crown (top) of the diamond, moving systematically across the stone to identify any inclusions or blemishes.
Five criteria determine the final grade:
- Size — how large are the clarity characteristics? Larger inclusions are more visible and lower the grade.
- Number — how many characteristics are present? More inclusions generally mean a lower grade, though a single prominent inclusion can be more detrimental than several minor ones.
- Position — where in the stone are the inclusions located? A characteristic directly under the table facet is far more visible than one near the girdle or beneath a crown facet. Table-centred inclusions also affect light performance by interfering with the return of light through the largest facet.
- Nature — what type of characteristic is it? A small pinpoint (a tiny included crystal) differs fundamentally from a feather (a fracture within the stone). Some inclusion types — such as large feathers near the girdle — can pose durability risks.
- Relief — how much contrast does the inclusion have against the surrounding diamond? A dark crystal inclusion stands out more than a white or transparent one, even at the same size.
The final grade reflects the combined effect of all five factors. It is a judgment call grounded in standardised criteria — not a mechanical formula.
The Clarity Grades
FL (Flawless)
No inclusions and no blemishes visible under 10x magnification. The diamond is completely clean inside and out at the standard grading power.
Flawless diamonds are exceptionally rare. Fewer than 1 % of gem-quality diamonds earn this grade. The premium reflects scarcity more than visual difference — a FL diamond looks identical to a VVS1 to the unaided eye. FL is a collector's grade, chosen for the knowledge of what it represents rather than what it shows.
IF (Internally Flawless)
No inclusions visible under 10x magnification. Minor surface blemishes only — typically a faint polish line or a tiny natural on the girdle. These surface characteristics are so minor that they do not affect transparency or light performance.
IF diamonds are nearly as rare as FL. In practical terms, the distinction between FL and IF is relevant only under magnification by a trained grader. Once mounted, the two grades are indistinguishable.
VVS1 and VVS2 (Very, Very Slightly Included)
Inclusions are present but extremely difficult to see under 10x magnification, even for a skilled gemologist.
- VVS1 — inclusions are minute and located in positions that make them difficult to find. A trained grader may need several minutes of careful examination to locate the characteristic. Typically a tiny pinpoint or a faint needle visible only from the pavilion side.
- VVS2 — inclusions are still very minor but slightly easier to detect under 10x than VVS1. The characteristic might be a small cloud, pinpoint cluster, or feather visible from the crown side under magnification.
VVS grades represent the highest clarity that includes internal characteristics. They carry a substantial premium over VS grades — often 15–25 % at the one-carat mark — for a difference that is invisible without magnification equipment.
When VVS makes sense: If you are purchasing a step-cut shape (emerald or Asscher) above 2 carats, where the large open facets can reveal inclusions more readily, VVS ensures absolute confidence that no characteristic will be visible. For round brilliants, the visual payoff of VVS over VS is negligible.
VS1 and VS2 (Very Slightly Included)
Inclusions are minor and range from difficult (VS1) to somewhat easy (VS2) to see under 10x magnification. They are not visible to the unaided eye.
- VS1 — a small included crystal, cloud, or feather that a trained grader can locate under 10x magnification with some effort. In most cases, the inclusion is off-centre or beneath a crown facet, which further reduces its visual impact.
- VS2 — the inclusion is more readily apparent under magnification. It might be a small crystal near the table or a cluster of pinpoints visible from the crown. Even so, VS2 characteristics are not visible to the naked eye in a well-cut stone.
The VS range is widely regarded as the technical sweet spot. You are paying for inclusions that require a loupe to find. In daily wear, a VS2 diamond is eye-clean — the term gemologists use when no inclusions are visible to a normal, unaided eye at a standard viewing distance of approximately 25 cm.
SI1 and SI2 (Slightly Included)
Inclusions are noticeable under 10x magnification. Whether they are visible to the unaided eye depends on the specific stone.
- SI1 — inclusions are easily found under magnification but typically not visible to the unaided eye, particularly in brilliant-cut shapes. Many SI1 diamonds are eye-clean, though this must be verified on a stone-by-stone basis. The type and position of the inclusion matter enormously at this grade.
- SI2 — inclusions may be visible to the unaided eye, especially in larger stones or step cuts. A trained observer may detect a dark crystal or prominent feather without magnification. However, some SI2 diamonds remain eye-clean depending on the nature and placement of their inclusions.
The SI range is where individual inspection becomes essential. Two SI1 diamonds can differ dramatically: one may have a white feather tucked under a bezel facet (invisible to the naked eye), while another has a dark crystal centred under the table (potentially noticeable). A grading report tells you the grade but not the story — you need to see the inclusion plot and, ideally, the diamond itself or a high-resolution image.
Czech market note: SI1 represents a significant value opportunity in the Czech market. The price difference between VS2 and SI1 at the one-carat mark is typically 15–20 %, and a carefully selected eye-clean SI1 will look identical on the hand. The CZK saved can fund a higher cut grade, which has a far greater impact on the diamond's visual performance. Ask for high-resolution imagery or video of any SI-grade diamond, and verify the inclusion position against the GIA inclusion plot.
I1, I2, and I3 (Included)
Inclusions are obvious under 10x magnification and visible to the unaided eye. At the lower end of this range, inclusions may affect the diamond's transparency, brilliance, or structural durability.
- I1 — inclusions are visible to the unaided eye. Depending on the type and position, they may affect brilliance by blocking or scattering light within the stone. Some I1 diamonds remain acceptable for jewellery use, particularly in smaller accent stones or designs where the setting partially obscures the inclusion.
- I2 — inclusions are easily visible and may significantly affect transparency and light performance. Large feathers in this range can also present durability concerns — a fracture near the girdle may be vulnerable to chipping during setting or daily wear.
- I3 — inclusions are prominent, typically affecting both beauty and structural integrity. Stones at this grade often appear cloudy or lifeless due to the extent of internal characteristics.
For engagement rings and significant jewellery, most gemologists and reputable retailers recommend I1 as the absolute floor for the centre stone. Below I1, the risk of durability issues and the visible impact on brilliance generally outweigh the cost savings.
EU consumer note: Under Czech and EU consumer protection law, sellers are obligated to disclose any characteristics that materially affect a product's fitness for purpose. For diamonds graded I2 or I3, a competent seller should clearly communicate whether durability is compromised. If a grading report is not provided with the stone, request one.
What Affects How Clarity Appears
Cut quality
A well-cut diamond returns more light to the eye, which can mask minor inclusions through brilliance and scintillation. Poorly cut stones with light leakage — dark areas where light escapes through the pavilion — create transparent windows that reveal inclusions more readily. This is why cut grade matters more than clarity grade for the diamond's visual performance.
Shape
Brilliant-cut shapes (round, oval, cushion, radiant) fragment reflected light into many small flashes, which helps conceal inclusions. Step-cut shapes (emerald, Asscher) have large, flat facets that function like clear windows, making inclusions more visible. Buy one to two clarity grades higher in step cuts than you would in a round brilliant for the same confidence of eye-cleanliness.
Carat weight
Larger stones have more visible table facets and greater material depth, both of which make inclusions easier to detect. An SI1 that is perfectly eye-clean at 0.70 ct may reveal its inclusion at 2.00 ct. Scale your clarity expectations with carat weight.
Inclusion type and colour
Not all inclusions at the same grade look the same. A dark crystal is more conspicuous than a white feather of identical size. A cloud (a cluster of tiny pinpoints) can be invisible individually but may create a hazy appearance if it spans a large area. Twinning wisps — complex inclusions formed by crystal distortion during growth — can be either subtle or prominent. The inclusion plot on the grading report identifies what is present; photographs or inspection reveal how it actually looks.
Practical Buying Advice
Prioritise eye-cleanliness, not grade. The goal is a diamond that looks clean to you — not the highest grade you can afford. A well-selected SI1 can deliver the same visual result as a VVS2 at a fraction of the cost.
Always inspect the inclusion plot. The GIA report maps every graded inclusion. Look for dark crystals under the table and feathers extending to the girdle. Characteristics near the edges or under crown facets are far less concerning.
Match clarity to shape and size. Round brilliants are forgiving — VS2 or SI1 is usually safe. Emerald and Asscher cuts need VS2 or higher for confident eye-cleanliness. Above 2 carats in any shape, consider stepping up one grade.
Do not overspend on FL–IF. Unless rarity or collection value is the objective, Flawless clarity offers no visible advantage over VVS or VS in daily wear. The premium funds a distinction that requires laboratory conditions to observe.
Request imagery for SI grades. Two SI1 diamonds can look very different. Ask for high-resolution photos, video, or an in-person inspection with a quality 10x loupe. A reputable seller will facilitate this.
Verify the report. Always confirm the diamond's clarity grade through a GIA, IGI, or HRD grading report. Verbal clarity claims without documentation should be treated with scepticism. See Choosing a Lab Report for guidance on evaluating different laboratories.
Summary
The GIA clarity scale grades diamonds across eleven levels — from Flawless (FL) to Included (I3) — based on the visibility of internal inclusions and surface blemishes under 10x magnification. The scale assesses five factors: size, number, position, nature, and relief of clarity characteristics. For most buyers, the VS2–SI1 range delivers eye-clean diamonds at a significant discount to higher grades. The key is to evaluate each stone individually, especially in the SI range, where two diamonds with the same grade can look materially different depending on what their inclusions are and where they sit. Cut quality, shape, and carat weight all influence how clarity appears in practice — a well-cut round brilliant is far more forgiving of inclusions than a step-cut emerald. Invest in seeing the stone, not just reading its grade.