Diamond Inclusions

Inclusions are the tiny features inside a diamond: minerals, fractures and irregularities trapped or formed as it grew. Blemishes are their equivalent on the surface. Together they decide a diamond’s clarity grade, from Flawless down to Included.

Inclusions are not flaws in the everyday sense. They are part of what makes each diamond unique, and they are the reason two diamonds can be told apart. What matters is whether you can see them, and whether any of them affect the stone’s strength.

A grading report lists the inclusions in a stone and marks them on a plot, a diagram of the diamond from above and below. These are the most common:

Crystal

A mineral trapped inside the diamond, sometimes another diamond. Can be white, clear or dark; dark crystals are the most visible.

Pinpoint

A tiny crystal, so small it looks like a dot under magnification. Usually invisible to the eye.

Cloud

A group of pinpoints close together. Small clouds are harmless; large ones can make a stone look slightly hazy.

Feather

A small fracture, often white and feathery in appearance. Most are harmless, but one that reaches the surface near the edge can be a weak point.

Needle

A long, thin crystal, like a tiny rod.

Twinning wisp

A ribbon of pinpoints, clouds or crystals formed where the crystal’s growth changed direction.

Indented natural

A small part of the original rough surface left on the polished stone, usually at the edge.

Chip or cavity

Small openings or breaks in the surface, from wear or from an inclusion that was polished away.

Lab-grown diamonds are graded on the same clarity scale and can contain inclusions as well. Their character can differ: diamonds grown by HPHT sometimes contain metallic inclusions from the growth process, and CVD diamonds can show small dark pinpoints of carbon. A grading laboratory identifies these as part of confirming origin.

Three things decide whether an inclusion matters: what it is, how large it is, and where it sits.

Position is often the deciding factor. An inclusion near the edge of the stone may be hidden under a claw or the setting. The same inclusion in the centre, under the table, will be the first thing you see. Dark inclusions show more than white or clear ones.

Durability is the other consideration. A large feather that reaches the surface, particularly near a point or the girdle, can be a weak spot if the stone is knocked. These are worth discussing before setting, and a careful setter will place claws to protect them.

For most people the practical aim is an eye-clean diamond: one with no inclusions visible to the naked eye, from a normal viewing distance, face up. In a well-cut brilliant, that is often achievable at VS2, and sometimes lower. Step cuts such as the emerald and Asscher show more, so they usually need a higher grade.

Read the plot, then look at the stone. The report tells you what is there; your eyes tell you whether it matters.