A Comprehensive Guide to Diamond Inclusions and Blemishes

In the world of gemology, perfection is the baseline, but the "fingerprints" of a diamond—its inclusions and blemishes—tell the true story of its origin. Whether a diamond was forged over millions of years deep within the Earth or grown in a high-tech laboratory, these internal and external characteristics are the primary markers of its identity.

While the word "imperfection" might sound like a flaw to avoid, gemologists view these features as technical data points that determine a stone's clarity grade, its history, and its unique character.

Inclusions vs. Blemishes: What’s the Difference?

It is essential to distinguish between where these marks are located, as they impact the diamond's value and grading in different ways.

Inclusions: These are internal features that formed inside the diamond during its creation. They are "trapped" within the crystal structure and cannot be removed without re-cutting the entire stone.
Blemishes: These are external marks that occur on the surface after the diamond has formed. These typically happen during the cutting and polishing process or through daily wear and tear.

The Internal Anatomy: Common Inclusion Types

Internal inclusions occur when foreign materials are trapped during growth or when the diamond's crystal lattice develops irregularly. Under 10x magnification, gemologists look for several specific patterns:

Crystals and Pinpoints: A Crystal is a mineral trapped inside the diamond. A Pinpoint is essentially a microscopic crystal that looks like a tiny dot.
Clouds: A cluster of many pinpoints that, when grouped together, create a hazy or "milky" appearance.
Feathers: A small internal crack or breakage. They are often white and feathery in appearance; however, if they reach the surface, they can pose a durability risk.
Needles: Long, thin crystals that look like tiny rods or needles at high magnification.
Graining: Internal lines or curves caused by irregular crystal growth. These can appear reflective or even colored.
Cavities and Knots: A Cavity is an angular opening, while a Knot is an inclusion that extends all the way to the diamond's surface.

Surface Scrutiny: Common Blemishes

Blemishes are confined to the surface. While they are often less critical than internal inclusions, prominent surface marks can still dull a diamond's luster.

Nicks and Chips: Small notches or shallow openings, usually found along the girdle (the edge) or the culet (the bottom point).
Scratch and Abrasion: Thin white lines or "fuzzy" edges caused by friction or contact with other diamonds.
Naturals: These are actually remnants of the original "skin" of the rough diamond left on the finished gem—a sign that the cutter tried to preserve as much weight as possible.

Natural vs. Lab-Grown Inclusions

While natural and lab-grown diamonds share the same chemical composition, their "growth stories" leave different marks.

Natural Diamonds act as time capsules. They often show distinctive growth lines and mineral inclusions that record millions of years of shifting pressure and temperature. These unique zoning patterns are virtually impossible to replicate in a lab.

Lab Diamonds are created in controlled environments, but they aren't always perfect. Their inclusions, often called "growth remnants," stem from the accelerated growth process. While a natural stone might have a mineral crystal, a lab stone might have a tiny remnant of the metallic catalyst used in the growth chamber.

Red Flags: Inclusions to Avoid

Not all inclusions are created equal. When shopping for a diamond—particularly in the SI1 or SI2 range—you should be cautious of "set-off" inclusions that could compromise the stone.

1. Durability Risks

Be wary of large feathers or deep cavities located near the points of fancy shapes (like the tips of a Marquise or the corners of a Princess cut). These create structural weak points that can lead to chipping if the stone is accidentally knocked.

2. Optical Killers

Dense clouds can make a diamond look "sleepy" or hazy, preventing it from reflecting light properly. Similarly, a large dark crystal situated directly under the "table" (the top flat facet) acts like a permanent black spot that is often visible to the naked eye.

Comparison Table: Internal vs. External Features

The following table summarizes the most common characteristics you will find on a GIA grading report.

Feature Type	Origin & Location	Common Examples	Impact on Diamond
Internal Inclusions	Formed inside during growth (natural or lab)	Crystals, Feathers, Clouds, Pinpoints, Needles	Affects clarity grade and light path; can impact durability if large.
External Blemishes	Confined to the surface; occurs after formation	Scratches, Chips, Nicks, Naturals, Abrasion	Impacts surface luster and polish grade; often removable by repolishing.

Diamond Inclusion FAQ

What do diamond inclusions look like?

Inclusions are internal characteristics that vary widely in appearance based on their type. They can look like tiny dots (pinpoints), thin rods (needles), or hazy white clusters (clouds). Some may appear as small mineral crystals trapped inside the diamond or as feathery white cracks.

Do lab grown diamonds have imperfections?

Yes, lab grown diamonds can have imperfections despite being created in a controlled environment. While they share the same chemical composition as natural diamonds, the accelerated growth process in a lab can lead to unique internal characteristics.

Are inclusions bad in a diamond?

Not necessarily. While "inclusion" may sound negative, it is simply the technical term for internal characteristics that form during the diamond's growth. Most diamonds have some level of inclusions; their impact depends on their size, color, and location.

What are the best inclusions to have in a diamond?

The "best" inclusions are those that are microscopic and invisible to the naked eye, such as minute pinpoints or needles found in VVS diamonds. These do not interfere with light performance or durability.

Why do lab grown diamonds have inclusions?

Lab diamonds develop inclusions due to inconsistencies during their accelerated formation process. This can include variations in temperature and pressure within the growth chamber or the presence of foreign particles.

What inclusions might be found in a lab grown diamond?

Lab diamonds feature distinctive patterns often referred to in documentation as "growth remnants." While they may be categorized as pinpoints or feathers, their specific appearance stems from the laboratory growth environment rather than millions of years of geological pressure.

How do inclusions affect diamond price?

Inclusions directly impact a diamond's clarity grade, which is a major factor in pricing. Diamonds with no visible inclusions (Flawless) command the highest premiums. As inclusions become more noticeable to the naked eye (Included grades), the price drops significantly due to reduced aesthetic appeal and brilliance.

Can inclusions get worse over time?

Most internal inclusions are permanent. However, surface-reaching inclusions, such as large feathers or deep cavities, can pose a durability risk. These structural imperfections can worsen with normal wear, potentially leading to chips or cracks if the diamond sustains a sharp impact.

Can inclusions be removed?

Inclusions are internal features trapped within the crystal structure and cannot be removed without cutting away portions of the gem, which would reduce its carat weight. In contrast, external blemishes can sometimes be removed through careful repolishing.