Black Diamonds

Introduction

Black diamonds break the rules that govern every other fancy colour. They are opaque, not transparent. Their colour comes from inclusions, not from trace elements or crystal defects. GIA grades them with a single designation — Fancy Black — because the intensity scale that maps Faint through Fancy Vivid has no meaning for a stone that lets no light through. They are diamonds by composition but something entirely different by visual character: dense, dramatic, and unapologetically dark.

What makes black diamonds additionally unusual is that the term covers two fundamentally different materials. Single-crystal black diamonds are standard diamond crystals so densely packed with dark inclusions that they appear black. Carbonado is something else entirely — a polycrystalline aggregate of microscopic diamond crystals whose origin remains one of geology's open questions. Both are diamond. Both are black. But they are not the same thing.

Key Points

The Colour Mechanism: Inclusions, Not Defects

Every other fancy diamond colour in this section traces to an atomic-scale cause: boron atoms absorbing red (blue), nitrogen absorbing blue (yellow), radiation displacing carbon atoms (green), lattice deformation disrupting light paths (pink, brown). Black diamonds are different. Their colour comes from inclusions — foreign mineral crystals trapped within the diamond during formation.

These inclusions are typically:

• Graphite — the most common, appearing as dark plates or sheets
• Magnetite — iron oxide crystals that absorb light and, in some stones, make the diamond slightly magnetic
• Hematite — another iron oxide with strong light absorption
• Native iron — metallic iron particles

The inclusions range from nanometre to micrometre scale and are so densely packed that they absorb or scatter virtually all incoming light. The diamond is not transmitting a dark colour — it is preventing light from passing through at all. This is why the concept of saturation (how strong the colour is) does not apply. There is no "light black" or "vivid black" — there is black or there is not.

GIA Grading: Fancy Black Only

GIA assigns a single grade to qualifying black diamonds: Fancy Black. The nine-point fancy colour scale (Faint through Fancy Vivid) is not used because those grades describe colour saturation and tone in transparent or translucent stones. A black diamond is neither — it is opaque.

The GIA Colored Diamond Identification and Origin Report for a natural black diamond will state:

• Colour: Fancy Black
• Colour origin: Natural (or will indicate treatment)

Fewer than 2,000 natural Fancy White and Fancy Black diamonds combined have been submitted to GIA since 2008. This is a small number relative to other fancy colours — reflecting both the niche nature of the market and the lower average value of black diamonds compared to blue, pink, or green.

Carbonado: The Other Black Diamond

Carbonado is a polycrystalline diamond material that is structurally and visually distinct from single-crystal black diamonds:

• Structure: Carbonado is composed of many tiny diamond microcrystals (typically 5 to 20 micrometres in size) fused together with non-diamond carbon, creating a porous, aggregate material. Under magnification, it looks like a sintered mass rather than a single crystal.
• Texture: Matte, granular, porous. Carbonado does not have the surface lustre of a polished single-crystal diamond.
• Geographic occurrence: Found only in alluvial deposits in Brazil and the Central African Republic. No other source has been documented. It is never found in kimberlite pipes — the volcanic conduits that deliver most diamonds to the earth's surface.
• Age: Carbonado is ancient, with ages estimated at 2.6 to 3.8 billion years.

The origin of carbonado is genuinely debated. Hypotheses include:

• Asteroid impact: A meteorite impact generating extreme pressures that converted carbon into polycrystalline diamond.
• Deep-earth formation: Conversion of carbon under mantle-like pressures, followed by tectonic transport to the surface.
• Interstellar origin: Some researchers have proposed that carbonado formed in space — in the carbon-rich envelope of a dying star or within the accretion disc of a protoplanetary system — before arriving on Earth via meteorite.

None of these hypotheses is universally accepted. The mystery is part of carbonado's appeal for collectors, but it also means that any definitive origin claim should be viewed with scepticism.

Natural vs Treated: The Critical Distinction

The black diamond market contains a significant proportion of treated stones. Treatment methods include:

• Irradiation — exposing a heavily included diamond to radiation, darkening the inclusions and the surrounding diamond material to achieve a uniform black appearance.
• HPHT treatment — high-pressure, high-temperature processing that can darken certain diamonds.

Treated black diamonds are substantially less expensive than natural Fancy Black diamonds. The treatment is permanent and does not affect durability, but it does affect value. A natural Fancy Black diamond, while not expensive by fancy colour standards, commands a meaningful premium over a treated stone of equivalent size.

For buyers, the GIA report is the safeguard. A natural Fancy Black diamond will have its colour origin described as "Natural." A treated stone will be described accordingly. Without laboratory documentation, the distinction is not reliably visible to the eye.

The Black Orlov

The Black Orlov is a 67.50 ct cushion-cut Fancy Black diamond, the most famous black diamond in history. According to legend, it was originally a 195-carat stone known as the "Eye of Brahma," set in a statue of the Hindu god in a temple in Pondicherry, India, and stolen by a monk.

Like the Hope Diamond's curse, the Black Orlov's legend includes a string of tragedies associated with its owners. The stone was reportedly recut into three pieces to break the curse. The 67.50 ct stone that survives is now set in a brooch surrounded by 108 colourless diamonds and suspended from a 124-diamond necklace.

The legend is colourful but unverifiable. What is documented is the stone's size — 67.50 ct is large for any fancy colour diamond — and its current setting, which has been exhibited at the American Museum of Natural History and the Natural History Museum in London.

Price and Value

Black diamonds sit at the affordable end of the fancy colour spectrum:

These prices reflect the reality that black diamonds, while visually dramatic, lack the transparency and light performance that drive premiums in other fancy colours. A black diamond does not sparkle in the conventional sense — it absorbs light rather than returning it. Its appeal is surface lustre, high contrast against white metal or colourless accent stones, and visual boldness.

Buying Considerations

• Verify natural vs treated. This is the single most important distinction in the black diamond market. A GIA report confirming natural colour origin is essential for any significant purchase.
• Understand you are buying a different visual experience. Black diamonds do not exhibit brilliance, fire, or scintillation in the way transparent diamonds do. They offer a metallic-to-adamantine surface lustre and a dramatic, opaque presence.
• Inspect the surface carefully. Heavily included black diamonds can be more fragile than transparent diamonds if inclusions create internal stress planes. Look for visible cracks, pits, or surface-reaching fractures that could affect durability.
• Setting matters. Black diamonds show most dramatically against white metals (platinum, white gold) or set with colourless diamond accents that provide contrast. They can feel heavy and undefined in yellow gold settings that do not provide visual separation.

Frequently Asked Questions

What causes the colour in black diamonds?

Black diamonds get their colour from dense populations of inclusions — graphite, magnetite, hematite, or native iron — that absorb or scatter all visible light. Unlike other fancy colours, the cause is physical particles rather than atomic-scale defects.

What is carbonado?

Carbonado is a polycrystalline diamond material composed of many tiny diamond microcrystals fused together. It is porous, matte-textured, and found only in Brazil and the Central African Republic. Its origin remains debated — hypotheses include asteroid impact, deep-earth formation, and even interstellar origin.

How can I tell if a black diamond is natural or treated?

You cannot reliably distinguish natural from treated black diamonds by eye. A GIA report confirming "Natural" colour origin is the essential safeguard. Treated black diamonds (produced via irradiation or HPHT) are substantially less expensive than natural Fancy Black.

Do black diamonds sparkle?

Black diamonds do not exhibit brilliance, fire, or scintillation like transparent diamonds. They offer a metallic-to-adamantine surface lustre and a dramatic, opaque presence. Their visual appeal comes from high contrast against white metals or colourless accent stones.

How much are black diamonds worth?

Natural Fancy Black diamonds (GIA certified) range $1,500–$3,000 per carat. Treated black diamonds are much more affordable at $200–$500 per carat. These sit at the affordable end of the fancy colour spectrum.

Related Reading

• Gray Diamonds — Inclusions can also create gray diamond appearance, bridging the gap between transparent and opaque.
• Fancy White & Opalescent — Another opaque/translucent category where inclusions define the diamond's character.
• Brown Diamonds — Another affordable fancy colour entry point with a transformed market reputation.
• Color Rarity & Certification — Why GIA certification matters for distinguishing natural from treated black diamonds.
• Fancy Color Market — How black diamonds fit into the broader fancy colour pricing hierarchy.

Summary

Black diamonds get their colour from dense inclusions — graphite, magnetite, hematite, or native iron — that absorb or scatter all light, making the stone opaque. GIA grades them as Fancy Black only, with no intensity scale. Carbonado is a distinct polycrystalline material found only in Brazil and the Central African Republic, with an origin that remains scientifically debated. The most important buyer distinction is natural versus treated: natural Fancy Black commands a meaningful premium, and a GIA report confirming colour origin is the standard safeguard. Black diamonds offer a bold, dramatic aesthetic at the most affordable end of the fancy colour market.