Diamond Education
Inclusions & Blemishes
Every mark named on a grading report, what it looks like, and, most usefully, which ones you should actually care about.
By 25karats · Updated 2026 · 7 minute read
Inclusions are internal characteristics formed while the diamond crystallized. Blemishes are external ones, on the surface, some natural and some created during cutting or wear. Together they set the clarity grade.
A grading report names each one, which is useful once you know what the names mean. The practical question is never “does this diamond have inclusions”, almost all do, but “do these particular inclusions matter?”
Inclusions are also, usefully, unique. The pattern in any given diamond is effectively a fingerprint. It is how a laboratory identifies a specific stone, and how you can confirm the diamond returned to you after a repair is the one you sent.
Inclusions, by type
Crystal inclusions
Other minerals, or smaller diamonds, trapped inside as the crystal grew.
| Name | What it is | Does it matter? |
|---|---|---|
| Crystal | A mineral crystal inside the stone, sometimes colorless, sometimes dark | Only if dark and under the table |
| Pinpoint | A very small crystal, appearing as a dot at magnification | Rarely: usually invisible to the eye |
| Needle | A long, thin crystal | Rarely, unless clustered or reflective |
| Cloud | A dense group of pinpoints reading as a hazy patch | Yes if large: a heavy cloud can make a stone look milky |
Breaks and fractures
The category most worth understanding, because it is the only one that can affect durability.
| Name | What it is | Does it matter? |
|---|---|---|
| Feather | A small internal crack, named for its feathery look | Yes if it reaches the surface, especially near the girdle |
| Bearded girdle | Fine hair-like feathers around the girdle from cutting | Sometimes, can give the girdle a fuzzy grey look |
| Bruise | A tiny impact point with root-like feathers spreading from it | Occasionally, check its position |
| Cavity | An opening in the surface, often where a crystal fell out | Yes, it traps dirt and can weaken the stone |
Growth characteristics
| Name | What it is | Does it matter? |
|---|---|---|
| Twinning wisp | A ribbon of distorted growth along a crystal plane | Rarely visible; common in fancy shapes |
| Internal graining | Faint lines or haze from irregular crystal growth | Yes if it dulls transparency, look for the word "hazy" |
| Indented natural | Original rough surface dipping below the polished surface | Rarely, if confined to the girdle |
| Laser drill hole | A fine tunnel drilled to reach and bleach a dark inclusion | Yes, this is a treatment and must be disclosed |
Blemishes: the surface
Blemishes sit on the outside. Some come from cutting, some from wear, and unlike inclusions, many can be polished away.
From cutting and polishing
Naturals are patches of unpolished rough left near the girdle to preserve weight. Extra facets are added to remove a blemish. Polish lines and wheel marks are grooves from the polishing wheel, and burn marks are a whitish haze from overheating. Mostly harmless; heavy polish marks can dull the surface.
From wear
Abrasions are fine nicks along facet edges, usually from diamonds rubbing against each other in storage. Nicks and chips are small breaks at an edge, typically from a knock. Pits are tiny surface cavities. Most abrasions and minor nicks can be polished out by a jeweler.
How to use this when buying
- Read the plot, not just the grade. The diagram on the report shows where each inclusion sits. Anything under the table deserves a closer look; anything near the girdle will probably be hidden by a prong.
- Search the comments for warning words. “Cavity,” “surface-reaching feather,” “laser drill hole,” and “clarity enhanced” all warrant a question before you buy.
- Ask whether it is eye-clean. Then verify it yourself, in person or on video. This matters more than the grade.
- Do not pay for invisible perfection. An eye-clean VS2 or SI1 looks identical to a flawless stone on a hand. See our clarity guide.
Inclusions in lab-grown diamonds
Lab-grown diamonds have inclusions too. They are crystals, and crystals grow imperfectly. The types differ somewhat from natural stones, reflecting how they were made rather than geology, but they are graded on exactly the same scale by the same laboratories. The practical difference is that at roughly 40–60% below natural prices, buying a cleanly graded stone costs far less, so there is little reason to accept an inclusion you can see. See our lab-grown diamond guide, or browse IGI-graded stones.
See it on real stones
Browse IGI-certified lab-grown diamonds by shape, carat, color, clarity and cut, at roughly 40–60% less than comparable natural stones.
More on diamonds: The 4Cs, Cut, Color, Clarity, Carat weight, Shapes, Certificates, and Conflict-free.