Types of Diamond Inclusions, Explained Simply

What an inclusion actually is

An inclusion is an internal feature that formed inside a diamond as it crystallized, often over a billion years, deep underground. Nearly every natural diamond has some kind of inclusion — a completely inclusion-free diamond (called "flawless") is genuinely rare. Inclusions are different from blemishes, which are surface-level characteristics like small scratches or nicks from cutting and handling. If you're new to diamond basics generally, our full diamond education guide is a good starting point before diving into clarity specifics.

The main types of inclusions

Feathers. Small internal cracks or fractures that can look feather-like under magnification. Most are tiny and stable, but a large feather close to the surface can be a durability concern worth discussing with a jeweler.

Crystals (or "included crystals"). Tiny mineral crystals that got trapped inside the diamond as it formed. These can be diamond crystals themselves or other minerals, and they typically appear as small dark or light dots.

Clouds. A cluster of extremely tiny pinpoint inclusions grouped closely together, which can sometimes create a slightly hazy area if dense enough. Light, scattered clouds are common and usually invisible without magnification.

Pinpoints. Extremely small crystal inclusions, smaller than the crystals described above, that look like tiny dots. Very common and almost always invisible to the naked eye.

Needles. Thin, elongated mineral inclusions that can look like tiny rods or fibers under magnification.

Knots. A crystal inclusion that reaches the diamond's surface, which can sometimes create a slightly raised or textured spot on the surface itself.

Graining. Internal growth irregularities that can look like faint lines, streaks, or a slight haziness, caused by irregular crystal growth rather than a foreign material.

Cavities and chips. Small openings or breaks, often related to a feather reaching the surface or handling damage, which are more of a durability note than a pure "inclusion" in the strictest sense.

Do inclusions affect how a diamond looks?

For the vast majority of diamonds in the middle clarity grades, no — inclusions are only visible under magnification and don't affect brilliance or sparkle to the naked eye. This is why many buyers intentionally choose a stone in the "eye-clean" range rather than paying a premium for a flawless grade that looks identical from arm's length. Our eye-clean diamond guide goes deeper on how to shop this way.

Inclusions matter more in a few specific cases:

• A large, dark inclusion positioned in the center of the stone (called a "table" inclusion) can sometimes be visible without magnification.
• A feather that's large and positioned near an edge or point (especially on fancy shapes like pear or marquise) can be a durability consideration, not just a cosmetic one.
• Very included stones (lower on the clarity scale) can appear slightly hazy or less brilliant overall.

How inclusions factor into a diamond's grading report

A certified grading report (from a lab like GIA or IGI) includes a clarity plot — a diagram showing the type, size, and position of the inclusions found in that specific stone. This is one of the most useful parts of a certificate, because it tells you exactly what you're getting rather than just a letter or number grade.

Frequently asked questions

Are inclusions the same as flaws or defects?

Not exactly — "inclusion" is the neutral, technical term. Most inclusions don't meaningfully affect a diamond's beauty or durability. The word "flaw" implies a problem, which isn't accurate for the vast majority of inclusions found in gem-quality diamonds.

Can inclusions get worse over time?

Generally no. Diamonds are extremely hard and stable, and normal, everyday wear doesn't cause internal inclusions to grow or spread. The exception is a stone with an existing large feather near the surface, which a jeweler might recommend protecting with a more secure setting style.

Do lab-grown diamonds have inclusions too?

Yes, though the type and pattern can differ slightly from natural diamonds because they form under different (faster, controlled) conditions. Lab-grown stones are still graded using the same clarity scale.

Should I avoid a diamond just because it has a feather inclusion?

Not automatically. Feather size, position, and depth matter far more than simply whether one exists. A trained eye (jeweler or gemologist) can tell you whether a specific feather is a real durability concern or a total non-issue.

What's the difference between an inclusion and a blemish?

Inclusions are internal; blemishes are on the surface, like small scratches, nicks, or polish lines. Both are considered in a clarity grade, but they're technically distinct categories.

So where does this leave you?

Inclusions sound scarier than they usually are. The real question isn't "does this diamond have inclusions" (almost all natural diamonds do) — it's "are these specific inclusions visible, and do they affect durability." That's a conversation a certificate and a trained eye can answer clearly.

How this plays into a custom design at Amana

Every stone Amana sources is reviewed by certified gemologists before it goes into a design, specifically so a client isn't guessing about what a clarity grade or a clarity plot actually means for their particular stone. Amana is a member of the Jewelers Board of Trade, and this kind of stone-level scrutiny is part of nearly 1,000 rings designed through the process so far.

Because the design and the stone are chosen together during your consultation, you get a plain-English explanation of exactly what's in your diamond — not just a grade on paper. If you're comparing shapes and want to know how inclusion visibility differs across cuts, our guide on the best diamond shapes for hiding inclusions is a useful next read, and our guide on why round diamonds cost more touches on how cut interacts with clarity needs. Design-plus-craftsmanship projects typically run $1,500–$4,000, with larger or more complex stones sometimes running past that. Book a consultation and we'll walk through a real certificate with you.