Diamond clarity measures how free a stone is from internal features (inclusions) and surface marks (blemishes), graded from Flawless down to Included on the scale used by every major laboratory. Here's the full diamond clarity chart — and, more usefully, a working gemmologist's honest advice on which grades are actually worth paying for.
The diamond clarity chart
| Grade | Meaning | What you'll actually see |
|---|---|---|
| FL | Flawless | Nothing, even under 10× magnification. Vanishingly rare. |
| IF | Internally Flawless | No inclusions at 10×; only trivial surface marks. |
| VVS1–VVS2 | Very, very slightly included | Inclusions a trained grader struggles to find at 10×. |
| VS1–VS2 | Very slightly included | Minor inclusions, visible at 10× with effort. Eye-clean. |
| SI1–SI2 | Slightly included | Noticeable at 10×; often still invisible to the naked eye. |
| I1–I3 | Included | Obvious at 10×, usually visible to the eye; can affect durability. |
Two things the chart doesn't tell you. First, grading is done at 10× magnification by a trained eye — not with the naked eye, and not at the 40× some retailers use for dramatic effect. Second, a grade is a judgement of size, number, position, nature and contrast of the inclusions combined, which is why two SI1 stones can look remarkably different.
What inclusions actually are
Inclusions aren't flaws in the sense of damage — they're birthmarks. A diamond crystallises deep in the mantle over unimaginable spans of time, and things happen along the way: tiny crystals of other minerals (or other diamonds) get swallowed, growth stress leaves feather-like fractures, clusters of pinpoints form hazy clouds. Each stone's internal map is unique — which is precisely how laboratories can identify an individual diamond years later. If you're curious about the deeper geology, I've written about how gemstones are actually born.
Where the smart money goes: the eye-clean rule
Here is the advice I give clients across the counter. Once a diamond is eye-clean — no inclusions visible to the naked eye at normal wearing distance — every clarity grade above that is invisible money. A VS2 and an IF can be optically identical on a hand; the difference lives only on the certificate and in the price, which can run 20–40% between those grades.
My sweet spot for most engagement rings is VS2 to SI1, checked stone-by-stone. The caveats:
Cut shape matters. Step cuts like the emerald cut have broad, open facets that hide nothing — go VS2 or better there. Brilliant cuts (round, oval, cushion) scatter light so effectively that a well-placed SI1 inclusion simply disappears.
Size matters. Inclusions are easier to see in larger stones. What's invisible in a half-carat can be findable in a two-carat, so grade expectations should rise with carat weight.
Position matters. An inclusion under a claw is free; a dark crystal dead-centre under the table is not. This is why I inspect every stone myself rather than buying off a certificate.
How to tell if a diamond is real
The honest answer: the at-home tricks you've read — fogging the stone, reading newsprint through it, dropping it in water — are unreliable folklore. Here's what actually works.
A handheld thermal tester identifies diamond by its extraordinary heat conduction, but be aware that moissanite also passes a basic thermal test — you need a multi-tester that checks electrical conductivity too (more in my moissanite vs diamond comparison). Under a 10× loupe, a gemmologist looks at girdle texture, facet junctions, the character of any inclusions, and for the tell-tale facet-edge doubling that betrays moissanite's double refraction. For any significant stone, the real answer is a certificate from a serious laboratory and a seller who'll put every claim in writing. At Lucano I only make certification claims on centre stones of 0.30 carats and up, where independent grading genuinely exists — a policy I'd encourage you to demand from any jeweller.
Clarity in context: it's the quietest of the 4Cs
Of the 4Cs, clarity is the one your eye notices least. Cut drives sparkle; colour shows against a white claw; carat is carat. My allocation for a fixed budget is almost always: maximise cut, then balance colour and carat, and let clarity sit at the lowest eye-clean grade the shape allows. That single decision routinely frees up a meaningful part of the budget on a ring — or upgrades a pair of diamond studs by a full size. For the complete picture, start with my Australian diamond buying guide.
And one more honesty note: lab-grown diamonds are graded on exactly the same clarity scale — the same birthmarks form in a reactor as in the mantle, just faster. Clarity advice doesn't change between natural and lab-grown; only the price does.
Diamond clarity FAQ
Which clarity grade is the best value?
VS2–SI1 for brilliant cuts, VS2 or better for step cuts like the emerald cut — always confirmed eye-clean on the actual stone, not assumed from the certificate.
Are SI diamonds a bad choice?
Not at all. Many SI1 stones are completely eye-clean, especially under one carat in brilliant cuts. The skill is choosing the right SI stone — that's precisely the sort of stone-by-stone vetting I do for bespoke clients.
Does clarity affect sparkle?
Barely, until you reach the I grades where dense inclusions can dull light return and even compromise durability. Above that, sparkle is overwhelmingly about cut quality.
Is a flawless diamond worth it?
As a rarity to own, perhaps. As something to wear, you're paying a large premium for a difference no human eye will ever detect. I'd rather see that budget go into cut quality.
