Are All Black Diamonds Treated?

 

The short answer: no. But almost every one you will ever see.

A black diamond does not look like a diamond. No fire, no sparkle, no brilliance in the classic sense. Instead a deep, closed black with a metallic surface lustre. It is precisely this break with expectation that makes it so compelling to many people.

And it is precisely this break that raises the question we are asked regularly in the showroom: is this even real, or has something been done to it?

The honest answer has two parts. Naturally black diamonds exist. They form deep in the earth's mantle, need the same billions of years as any other diamond and are rarer than colourless material. At the same time: what ends up in rings, ear studs and bracelets is colour treated in the overwhelming majority of cases. The Gemological Institute of America puts it unambiguously in its own guide, stating that many of the black diamonds used in jewellery and engagement rings today have been treated.

It is real diamond. It is real carbon. The deep black colour simply does not come from the earth, in the end it comes from the treatment.

How a diamond turns black in nature

In diamonds, colour almost always comes from foreign atoms in the lattice. Nitrogen makes yellow. Boron makes blue. Lattice distortion makes pink. Black works differently.

Inclusions instead of pigment

A naturally black diamond is not coloured through. It is permeated with countless tiny inclusions of graphite, pyrite or hematite, distributed across the entire volume, and they swallow the light before it can escape again. What you see is not a black body, but a colourless diamond packed so densely with dark material that nothing passes through any more.

That also explains the distinctive lustre. The light is not refracted inside and returned, as happens in a cut brilliant. It is reflected off the polished surface. The result looks more like polished metal than like a gemstone.

The special case: carbonado

Alongside this sits carbonado, a polycrystalline variation. It consists not of a single crystal but of a dense aggregate of countless tiny diamonds in random orientation, permeated with carbon, graphite and metal oxides. Carbonado occurs almost exclusively in Brazil and Central Africa, and in alluvial deposits rather than in kimberlite pipes. Its origin has still not been conclusively explained.

For jewellery, carbonado is difficult. The polycrystalline structure can only be cut and polished precisely with considerable effort, because the hardness runs differently in every direction. The International Gem Society also points out that this very randomness of crystal orientation brings a structural instability with it.

Why the material is so scarce

What is wanted is an even, deep black without grey or brownish zones, in usable size, cuttable, without fractures running right through. This combination is exceptionally rare. Anyone familiar with fancy coloured diamonds already knows the principle: rarity never lies in the colour alone, but in colour plus evenness plus size plus workability. We have written a blog about this in detail elsewhere, for fancy coloured diamonds in general and for Argyle Pink diamonds.

The routes to treated colour

Treated black diamonds start out as diamonds with very heavy inclusions that are hard to classify. Heavily included, fractured grey or brown rough, hard to use for colourless applications because neither clarity nor colour carries. Treatment gives this material a second use.

High temperature treatment

The most widespread method. The diamond is heated at low pressure to temperatures above roughly 1,300 degrees Celsius. Within the existing fractures and cleavages, carbon converts into graphite. This graphite is black and opaque. It coats the internal fracture network from the inside out and renders the entire diamond opaque.

That explains an important characteristic: the more fractured the starting material, the better the result. A clean diamond cannot be blackened this way at all. The treatment needs the flaws it conceals.

Irradiation

The second route runs through particle accelerators. Irradiation alters the crystal lattice and produces an extraordinarily dark green. The GIA describes it precisely: so dark that it appears black to the naked eye. This is usually followed by a heat treatment to reduce residual activity.

And here lies the single most useful identifying feature. An irradiated diamond is not black. It is very dark green or dark blue and merely appears black. Under a strong transmitted light source, this becomes visible.

Coating

Rarer, and unsuitable for fine jewellery, is surface coating. Here the colour is applied rather than created. A coating is not permanent. It wears away at the edges and reacts to ultrasonic cleaning and to repair heat. For a ring worn every day, it is out of the question.

Lab grown in black

Then there is a third category that is rarely separated cleanly: laboratory grown diamonds that are subsequently treated, or deliberately grown with a high inclusion content. In material terms this is diamond, chemically identical, but neither naturally grown nor naturally coloured. If you want to read up on the fundamental differences, you will find them in our comparison of lab grown and natural diamonds.

How to recognise a treatment

Four checks, in ascending order of reliability. The first three you can carry out yourself. The fourth is the only one that gives certainty.

1. The look against the light

Hold the diamond against a strong, focused light source, ideally at the thinnest point of the girdle. A treated diamond often lets more light through than you expect, and that light is rarely neutral. It pulls towards green or blue. A naturally black diamond stays denser and more neutral.

2. With a loupe

Under magnification the structural difference becomes visible. Natural material shows an irregular, three dimensionally staggered field of individual dark inclusions with recognisable boundaries. Treated diamonds show more of a flat network of filled fractures following the course of the cleavages. The colour looks strikingly even, almost too even.

3. The surface and the edges

Check the facet edges and the girdle. Uneven colour distribution, chipped edges or a matt looking zone along the girdle point to a great deal of fractured material, and therefore to treated goods. With a coating, wear shows up in exactly those places first.

4. The gemmological certificate

The only reliable answer. Worth knowing: black diamonds fall outside the usual clarity scale and therefore do not receive a classic diamond report with a clarity grade. The GIA issues a Colored Diamond Identification and Origin Report for them instead. That report answers exactly one question in full: is the colour natural in origin or treated?

Look at the wording on colour origin in the document. Terms such as treated, treated colour or enhanced are a declaration, not small print. If there is no statement on colour origin at all, the question has not been answered, it has been left open. Why a report alone still guarantees no quality is something we covered in depth when addressing how to choose diamonds properly.

The direct comparison

Treated is not worse. It is something else.

At this point the discussion often turns moral, and that is a mistake. A colour treatment is not a fraud. It is a recognised process with one clear condition: it must be disclosed.

What actually changes through treatment is not the beauty. It is three other things.

The price. The International Gem Society quotes thousands of US dollars per carat for naturally black material and figures of a few hundred US dollars per carat for treated material. Anyone paying the natural price and receiving treated material has a real problem. Anyone knowingly buying treated material at the treated price has made a good deal.

The retention of value. Treated material is reproducible at will. There is rough for it in abundance. Under these conditions no resale value develops. That is unproblematic as long as you know it and do not regard the ring as an investment.

The resilience. The point that actually counts in daily wear.

What this means for your ring

Hardness and toughness are two different properties. A black diamond has the full Mohs hardness of 10. Nothing can scratch it. That does not make it tough.

The International Gem Society puts it plainly: despite their hardness, black diamonds can be very brittle and prone to fracturing, because they are typically heavily included and the internal fractures weaken the structure. A knock in the wrong place can be enough. With treated material there is the added fact that the very fracture network carrying the colour is also the breaking point.

This is not an argument against black diamonds. It is an argument for the right setting.

Setting: protected rather than exposed

A black diamond does not belong in a high set prong mounting with an exposed girdle. It belongs in a construction that encloses the girdle and channels impact energy into the setting rather than into the diamond. Bezel settings and semi closed settings do exactly that. If prongs are wanted, then generously dimensioned and worked flat, with full contact. Which designs exist and how they behave in daily wear can be found in our overview of the different prong types.

The setting work itself comes down to the hand. Pressure has to be built up evenly and in measured steps. A black diamond forgives no abrupt approach. In our Augsburg workshop we therefore always work these settings by hand, rather than through a standard casting with a prong pressed over afterwards.

Later work on the ring

Here is the point almost nobody raises at the sales counter. Any later work on the ring that involves heat is delicate with a treated diamond. Resizing, solder joints, replacing worn prongs, and aggressive cleaning processes too. Coatings will certainly suffer damage, and with other treatments caution is the only correct stance.

The consequence is simple: the diamond is removed from the setting before such work and reset afterwards. That costs time and money. It is the reason the setting should be right from the beginning, and why it is worth thinking about later repair and recutting before the purchase rather than after it.

How we work with black diamonds

Our rule is short: the colour origin is on paper before we talk about design.

In concrete terms, that means this. For every black diamond we declare whether the colour is natural or treated, and we do so before naming a price, not afterwards. We tell you which process was used, as far as the laboratory report shows it. And we choose the setting according to the stress the ring will actually see, not according to what looks lightest in a photograph.

For engagement rings with a black centre diamond, that generally means a protected setting and a carefully planned underbezel. For wedding rings and wedding bands, which are worn permanently and take considerably more, we go further still and set smaller carat weights deep and flush.

If you are after the effect of contrast, combine black diamonds with colourless ones from our selection of natural diamonds. If you would rather play with shape, you will find the right cuts in diamonds in special shapes. And if you want to work through the build yourself, you can do so in the configurator, where every change shows in the price immediately.

Frequently asked questions about black diamonds

Are all black diamonds treated?

No. Naturally black diamonds exist, but they are very rare. In the jewellery trade the large majority are colour treated. Without a laboratory report the colour origin cannot be determined with certainty.

Is a treated black diamond a real diamond?

Yes. It is natural diamond with the full Mohs hardness of 10. Only the colour was changed, not the material. The term treated refers to the colour, not to authenticity.

How is a diamond coloured black?

Two processes dominate. In high temperature treatment above roughly 1,300 degrees Celsius, carbon within the existing fractures converts into black graphite. In irradiation, a particle accelerator produces an extremely dark green that appears black to the eye.

What is a carbonado?

Carbonado is a polycrystalline variety of diamond consisting of many tiny, randomly oriented crystals. It occurs almost exclusively in Brazil and Central Africa. Its formation has still not been conclusively explained scientifically.

How do I tell whether my black diamond is treated?

Hold it against a strong light source. If a dark green or dark blue shimmer shows at the thin edges, that points to irradiation. The only reliable evidence is a laboratory report stating the colour origin.

Does a black diamond get a GIA certificate?

Not in the usual form. Black diamonds lie outside the normal clarity scale and therefore receive no classic report with a clarity grade. The GIA issues a Colored Diamond Identification and Origin Report instead, which documents the colour origin.

What does a black diamond cost?

The range is wide. Naturally black material is quoted at thousands of US dollars per carat depending on quality, treated material lies considerably below that. What matters is that you know which of the two categories you are paying for.

Is a black diamond suitable for an engagement ring?

Yes, if the setting is right. Black diamonds are hard, but brittle and prone to fracturing because of their inclusion density. A bezel setting, or a generously dimensioned flat prong setting, protects the girdle effectively. At Designer Diamonds we plan exactly this construction through before production, rather than adjusting it afterwards.

Can a black diamond fade?

High temperature treatment and irradiation are permanent and do not fade in normal wear. A surface coating, on the other hand, wears away at the edges and reacts sensitively to heat and aggressive cleaning. That is why we do not work with coated material.

Can a ring with a black diamond be resized?

Yes, but not with the diamond in the setting. The heat involved can damage treated material. Done properly, the diamond is removed beforehand and reset afterwards.

Does a black diamond sparkle?

Not in the classic sense. Since no light penetrates the interior, neither brilliance nor fire develops. What you see is a metallic looking surface lustre on the polished facets.

Do black diamonds also exist as a lab grown variant?

Yes. Laboratory grown diamonds can equally be treated or deliberately grown with a high inclusion content. Make sure an offer separates two statements: the origin of the crystal and the origin of the colour.

How do I know I am being advised correctly?

Ask for the colour origin before the price is named. Anyone who avoids the question, or answers it only when pressed, has already given you an answer. With us the declaration comes at the start of the conversation, in Munich as in Augsburg.

How do I care for a ring with a black diamond?

Lukewarm water, mild soap, a soft brush. No ultrasonic cleaning, no steam cleaning, no chemical dips. Take the ring off for sport, gardening and anything where it can strike a hard edge.