Diamond Types: Why All Diamonds Are Not Alike

The term "diamond type" can be used in two different ways, depending upon the context.

In gemology and diamond science, diamond type has a precise technical meaning. Diamonds are classified according to the atomic impurities and defects present within their crystal structure. The principal scientific classifications are Type Ia, Type Ib, Type IIa and Type IIb.

In the jewelry trade and general consumer use, the term "diamond types" is also used more broadly to describe categories such as natural diamonds, lab-grown diamonds, rough diamonds, fancy-color diamonds, treated or enhanced diamonds, and industrial diamonds.

These two systems describe different things. The scientific system explains a diamond's atomic makeup and impurity structure, while the broader commercial system describes its origin, condition, appearance, treatment or intended use.

A single diamond can therefore belong to both systems at the same time. For example, a natural blue diamond may be commercially described as a natural fancy-color diamond while scientifically being classified as a Type IIb diamond.

1. Scientific Diamond Type

Scientific diamond type is based primarily on the presence, absence and arrangement of trace impurities within the diamond crystal lattice.

Nitrogen and boron are especially important because they can influence the way a diamond absorbs light and, in some cases, its visible color and electrical properties.

The four principal scientific diamond types are:

• Type Ia - aggregated nitrogen
• Type Ib - isolated nitrogen
• Type IIa - little or no measurable nitrogen or boron
• Type IIb - measurable boron

2. Commercial and Descriptive Diamond Types

In jewelry, retail and general educational material, the phrase "diamond types" is often used in a broader descriptive sense.

These categories may include:

• Natural diamonds
• Lab-grown diamonds
• Rough diamonds
• Polished gem diamonds
• Fancy-color diamonds
• Treated or enhanced diamonds
• Industrial diamonds

These categories describe characteristics such as origin, physical condition, color, treatment or use, rather than the diamond's atomic impurity classification.

Why the Distinction Matters

Understanding these two meanings prevents confusion when reading gemological reports, jewelry descriptions or educational material.

For example, the description "lab-grown diamond" tells you how the diamond originated, but it does not by itself tell you whether the diamond is scientifically Type Ia, Type Ib, Type IIa or Type IIb.

Likewise, the designation "Type IIa" describes aspects of a diamond's atomic structure, but it does not by itself tell you whether the diamond is natural or laboratory-grown, colorless or fancy-colored, treated or untreated.

Throughout this page, both meanings are discussed: first the scientific gemological classifications, and then the broader commercial and descriptive categories.

Major Diamond Types and Categories

Diamonds can be described in several different ways. The montage above illustrates broad commercial and descriptive categories, while the scientific classifications discussed below are based on the diamond's atomic structure.

How Scientific Diamond Types Are Classified

Diamond is composed primarily of carbon atoms arranged in a cubic crystal structure.

During diamond formation, small amounts of other elements can enter the crystal lattice. Nitrogen is the most common impurity found in natural diamonds, while boron is associated with some rare blue diamonds.

The presence, absence and arrangement of these impurities determines the diamond's scientific type.

Gemological laboratories can identify diamond type by studying how the stone absorbs infrared, visible and ultraviolet light.

Diamond Type and Appearance

Scientific diamond type can influence color and optical behavior, but type alone does not determine a diamond's overall beauty or value.

Value is influenced by many factors, including:

• Carat weight
• Color
• Clarity
• Cut quality
• Natural or laboratory-grown origin
• Treatments
• Rarity
• Market demand

Type I Diamonds

Type I diamonds contain measurable nitrogen within their crystal structure.

They make up the great majority of natural diamonds and are divided into two major categories: Type Ia and Type Ib.

Type Ia Diamonds

Type Ia is the most common scientific type among natural diamonds.

In Type Ia diamonds, nitrogen atoms occur in aggregated groups rather than remaining primarily as isolated individual atoms.

These nitrogen-related defects can influence how the diamond absorbs light and may contribute to yellow or brown coloration in some stones.

Many Type Ia diamonds are colorless or near-colorless, while others exhibit visible body color.

Type IaA and Type IaB

Type Ia diamonds can be divided further according to the arrangement of nitrogen atoms.

Type IaA diamonds contain nitrogen primarily in paired arrangements known as A centers.

Type IaB diamonds contain larger nitrogen aggregates known as B centers, generally involving groups of nitrogen atoms associated with a vacancy in the crystal lattice.

Many natural diamonds contain a mixture of both IaA and IaB characteristics.

Type Ib Diamonds

Type Ib diamonds contain nitrogen atoms that are largely isolated rather than grouped into aggregates.

Type Ib diamonds are much less common in nature than Type Ia diamonds.

Isolated nitrogen can absorb light in the blue portion of the visible spectrum, causing some Type Ib diamonds to appear strongly:

• Yellow
• Orange-yellow
• Brownish-yellow

Some intensely colored natural yellow diamonds are associated with Type Ib characteristics.

Type II Diamonds

Type II diamonds contain little or no measurable nitrogen detectable by standard infrared absorption techniques.

They are considerably less common than Type I diamonds and are divided into:

• Type IIa
• Type IIb

Type IIa Diamonds

Type IIa diamonds contain very little measurable nitrogen or boron and are among the most chemically pure natural diamonds.

Many exceptional colorless diamonds belong to this category.

Type IIa diamonds can also display color caused by structural distortion within the crystal lattice.

These colors can include:

• Pink
• Brown
• Purple
• Gray

Famous Type IIa Diamonds

Several historically important diamonds have been identified as Type IIa.

Examples include diamonds associated with:

• The Cullinan
• The Koh-i-Noor
• The Graff Pink

Type IIa classification does not by itself make a diamond superior to every Type I diamond. Cut, color, clarity, size and individual beauty remain essential considerations.

Type IIb Diamonds

Type IIb diamonds contain measurable amounts of boron within the crystal lattice.

Boron absorbs portions of visible light in a manner that can produce blue or blue-gray coloration.

Type IIb diamonds are rare and are also unusual because they can exhibit measurable electrical conductivity.

Some Type IIb diamonds are strongly blue, while others may be grayish-blue or nearly colorless.

Famous Type IIb Blue Diamonds

Several famous blue diamonds are associated with the Type IIb category.

One of the best-known examples is the Hope Diamond, whose blue color is associated with boron-related absorption.

Blue diamonds are among the rarest natural fancy-color diamonds, although color intensity, size, clarity and provenance can vary greatly from stone to stone.

Scientific Diamond Types vs. Commercial Diamond Categories

The term diamond type has a precise scientific meaning, but the word "type" is also used more broadly in the jewelry trade.

For example, buyers may hear references to natural, lab-grown, fancy-color, treated, rough or industrial diamonds. These are useful commercial or descriptive categories, but they are not the same as the scientific Type I and Type II classification system.

Natural Diamonds

Natural diamonds formed within the Earth under conditions of high pressure and temperature over very long periods of geological time.

They are brought toward the Earth's surface through geological processes and are recovered from primary deposits or secondary deposits such as alluvial gravels.

Natural diamonds can belong to any of the major scientific types, including Ia, Ib, IIa and IIb.

Lab-Grown Diamonds

Lab-grown diamonds are real diamonds produced in controlled technological environments rather than formed naturally within the Earth.

They have the same basic carbon crystal structure as natural diamonds and can exhibit comparable hardness, brilliance and optical properties.

Laboratory-grown diamonds are commonly produced using processes such as:

• High Pressure High Temperature (HPHT)
• Chemical Vapor Deposition (CVD)

Their growth characteristics and impurity patterns can differ from those of natural diamonds, allowing trained laboratories to distinguish them.

Rough Diamonds

Rough diamonds are diamonds in their uncut and unpolished state.

Natural rough crystals can appear as octahedra, cubes, irregular crystals, fragments or other forms.

Before cutting, a rough diamond is studied carefully to determine how its crystal shape, inclusions and internal strain may affect the final polished gemstone.

Polished Gem Diamonds

Gem-quality diamonds are cut and polished to reveal their beauty and optical performance.

A finished diamond may be fashioned into round, princess, oval, cushion, emerald, radiant, pear, marquise, heart, Asscher and many other shapes.

Once polished, its value is influenced by the Four Cs: carat weight, color, clarity and cut.

Fancy Color Diamonds

Fancy color diamonds display natural body colors strong enough to be evaluated outside the traditional colorless-to-light-yellow grading range.

Natural fancy colors can include:

• Yellow
• Pink
• Blue
• Green
• Orange
• Brown
• Purple
• Red
• Gray

The cause of color differs by diamond. Nitrogen, boron, crystal deformation, radiation-related defects and other structural features can all influence color.

Treated or Enhanced Diamonds

Some natural or laboratory-grown diamonds undergo treatments designed to alter their appearance.

Treatments may be used to modify color or, in some cases, reduce the visibility of certain clarity characteristics.

Examples of treatments can include:

• High Pressure High Temperature treatment
• Irradiation
• Annealing
• Fracture filling
• Laser drilling

Significant treatments should be disclosed when a diamond is sold.

Industrial Diamonds

Diamonds are valued not only as gemstones but also for their exceptional physical properties.

Because diamond is extremely hard, industrial diamonds are used in:

• Cutting tools
• Grinding wheels
• Drilling equipment
• Abrasives
• Precision machining

Industrial diamond may be natural or synthetic and does not need the visual qualities required of a gemstone.

Diamond Type Classification Table

What Diamond Type Means to a Buyer

Scientific diamond type can be fascinating and can help explain a diamond's color, origin and physical behavior, but it should not be considered in isolation when buying a gemstone.

A Type IIa diamond is not automatically more beautiful than a Type Ia diamond, and a Type I diamond is not automatically lower quality.

For most jewelry buyers, the most important considerations remain the diamond's:

• Overall appearance
• Cut quality
• Color
• Clarity
• Carat weight
• Origin
• Treatment status
• Independent grading report

Explore More Diamond Information

The Four Cs   |   Carat Weight   |   Color   |   Clarity   |   Cut   |   Diamond Shapes

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