The traditional white or colourless diamonds that we all love to see shine in for example a classical engagement ring, are formed through a complex process in which carbon molecules are exposed under high pressure close to the core of the earth. However we see that women are increasingly opting for a ring with coloured diamonds or other diamond jewellery including beautiful gemstones. With colour you also impress. No wonder that the customer demand is increasing. Nowadays the most breathtaking coloured diamonds are processed in equally impressive jewellery. But how are coloured diamonds made? And in which colours do they occur?

How are coloured diamonds made?

All diamonds go through the same process, as well as coloured ones. The colours are created in a different way. During the crystallization process, the final colour is each time determined by a different nature element. The rare red and pink diamonds occur under intense pressure and heat under the crust. Blue diamonds occur by the addition of boron, a black semi-metal. This way every diamond has its own colour. In addition, every colour gradation is possible. Which makes any coloured diamond unique among its kind. Hence a ring including coloured diamonds is so expensive. But for that price you will have something very unique.

Provenance and certification: how to verify a coloured diamond's origin

Understanding a coloured diamond's origin and whether its colour is natural or altered matters for rarity, value and long-term behaviour. Natural, treated and lab-grown coloured diamonds can look similar at first glance, but their origin affects how they should be documented and priced. Clear answers protect the buyer and the piece itself.

Recognising natural versus treated or lab-grown stones

Natural coloured diamonds get their hue during geological formation. Treated stones have had their colour changed after extraction using methods such as high-pressure high-temperature treatment, irradiation or surface coatings. Lab-grown coloured diamonds are produced in controlled conditions and can show the same optical characteristics as natural stones. Each category is legitimate, but disclosure and documentation must be precise.

What certificates should state

A reliable gemological report should say plainly whether the colour is natural, the result of a treatment, or laboratory-grown. The report should include measurements, carat weight, and, where relevant, plotted diagrams of inclusions or colour zoning. It should also state which tests were used and explain any conclusion about origin or treatment. Explicit wording such as “natural colour” or the specific treatment named is preferable to vague phrasing.

Commonly accepted laboratories and what they report

Established independent laboratories are known for consistent reporting on coloured diamonds. Their reports typically note whether colour is natural or treated, describe any enhancements, and include diagrams or spectroscopy results when appropriate. Sellers should be able to provide the original laboratory report linked to the exact stone.

A practical checklist to request before purchase

1. Request the original lab report for the exact stone, not a duplicate or a generic certificate.
2. Confirm the report specifies whether the colour is natural, treated or laboratory-grown.
3. Ask for exact measurements, carat weight and any plotted inclusion or colour-zoning diagram.
4. Enquire which tests were performed (for example, spectroscopy or inclusion analysis) and whether treatment detection was conclusive.
5. Request the stone's provenance chain-of-custody if available.
6. If multiple stones are sold as a matched set, ask for individual reports for each stone.

Red flags that suggest undisclosed treatment or uncertainty

Be cautious when documentation is vague or missing. Warning signs include certificates that omit treatment statements, reports not linked to the specific stone, reluctance to show the original report, or batches of stones with unnaturally uniform colour and no individual documentation. Phrases like “colour appearance” without a clear origin statement should prompt further questions.

Buying checklist for a coloured-diamond ring

• Confirm the type of stone: ask explicitly whether the diamond is natural, treated, or laboratory-grown and insist on clear wording in the documentation.
• Insist on the original laboratory report for the specific stone, showing measurements, carat weight and any plotted diagrams of inclusions or colour zoning.
• Verify the report states the colour origin or, if treated, specifies the treatment type and detection methods used.
• Request information on tests performed (for example, spectroscopy or inclusion analysis) so you understand how the conclusion was reached.
• For matched sets, obtain separate certification for each stone rather than a single combined statement.
• Follow Baunat quality guidelines: confirm metal specifications meet premium standards and ensure diamond specifications comply with brand quality; do not accept vague material descriptions.
• If provenance or prior ownership matters to you, ask for chain-of-custody or sourcing details where available. This checklist helps ensure transparency and protects long-term value without prescribing purchase decisions. Clear documentation and open seller communication are the most effective safeguards when buying coloured diamonds.

How coloured diamonds form: a step-by-step geological timeline

A short timeline makes it easier to follow how carbon deep in the Earth can turn into a diamond that shows blue, yellow, pink or red. Below is a stepwise account of the geological events and microscopic changes that create those colours, with short examples of what to look for in the stone.

Step 1, diamond formation in the mantle

Diamonds grow in the upper mantle, typically at depths around 140–200 kilometres, where high temperature and pressure force carbon atoms into a dense tetrahedral lattice. Growth is extremely slow on human timescales, taking millions to many millions of years. The crystal forms in layers, producing growth zones that later influence how colour and inclusions appear.

Step 2, trace elements and impurities enter the crystal

Pure diamond is carbon, but tiny amounts of other elements incorporated during growth change how the crystal absorbs light. For example, boron atoms replacing carbon produce blue absorption features and yield blue diamonds. Nitrogen in certain aggregation states gives yellow tones. The final hue depends on which element is present, how it is distributed through the growth zones and its concentration  -  even minute amounts can be visible.

Step 3, plastic deformation and lattice defects (pink and red diamonds)

Not all colours come from foreign atoms. Pink and red diamonds usually get their colour from plastic deformation  -  permanent distortions of the carbon lattice caused by extreme stress after initial growth. That stress creates defects and strain that change how light passes through the stone, producing pink to red hues. These diamonds often show characteristic strain patterns and zonal colouration under specialized lighting.

Step 4, post-growth modification: natural radiation and damage

Some colours originate from natural radiation, either while the diamond remains in the ground or from nearby radioactive minerals. Radiation can displace atoms in the lattice, creating defects that absorb specific wavelengths and produce green or other colours. In the trade, similar colours can be produced artificially by irradiation followed by controlled heating; detecting treatment is an important point for certification.

Observable indicators  -  what to look for under the loupe or in reports

• Growth zones and colour zoning: Natural growth zoning often appears as faint bands or areas of different colour intensity. In pink diamonds, for example, colour is often concentrated along growth planes that reflect the direction of lattice strain.
• Inclusions and mineral traces: The type and pattern of inclusions point to the mantle environment. Certain mineral inclusions are typical of deep-formed stones and support a natural origin.
• Strain patterns under cross-polarized light: Plastic deformation leaves interference colours and strain lines visible under polarized light, a useful diagnostic for pink/red diamonds.
• Spectral features: Instruments reveal absorption lines or bands linked to boron, nitrogen or radiation-related defects; these signatures help labs determine the cause of the colour.

Real-world example

• Pink diamonds: Colour mainly from lattice strain; often show distinct pink zoning and strong strain patterns under polarized light.
• Blue diamonds: Boron impurities in the lattice produce the blue hue; spectroscopy typically shows boron-related absorption.
• Yellow to brown diamonds: Nitrogen in specific aggregated forms causes yellow tones; the distribution of nitrogen and growth-related features influence intensity.

Why this matters for value and identification

Knowing the sequence of formation and the visible indicators it leaves helps gemologists and buyers distinguish natural, treated and lab-grown stones, and explains why some stones command higher prices. Colour that results from natural geological processes, especially rare mechanisms like lattice deformation or deep-borne boron incorporation, contributes to a diamond's rarity and appeal. When colour is due to treatment, this should be disclosed on documentation and can affect valuation.

In short, a diamond's colour records both its birth and its subsequent geological history; reading that record means looking for growth zones, trace-element signatures and deformation features that reveal how the hue formed.

Certification and how to verify a coloured diamond's origin

Reliable documentation is essential when buying a coloured diamond. Laboratory reports from established gemological institutes describe whether a stone is natural, treated or laboratory-grown, and list the tests used to reach that conclusion. Knowing what to look for on a certificate helps you interpret a stone's origin with confidence.

Common certificates and what they state

Leading laboratories such as GIA, AGS and IGI issue reports for coloured diamonds. These reports typically record the stone’s basic characteristics, note any treatments, and may include a plotted diagram and comments on origin. For coloured diamonds the key statements are whether the colour is natural, the presence of treatments (HPHT, irradiation or annealing) and any remarks about laboratory origin.

How treatments are reported

Reputable labs will clearly identify treatments when detected. Typical wording to note includes statements that the stone is “treated” or that colour was “enhanced” by specific processes. HPHT and irradiation are two common treatments that can change colour; their presence should be plainly reported on the certificate.

Tests and indicators used in verification

• Spectroscopy: Analyses the light absorption pattern of the diamond to detect signatures associated with elements like boron or nitrogen and with certain lattice defects.
• Fluorescence: Responses to ultraviolet light can support identification; particular luminescence behaviours are characteristic of specific origins.
• Inclusion and growth-pattern analysis: Microscopic examination of inclusions and growth zoning provides clues about mantle formation versus lab growth. Many reports include photomicrographs or descriptions of these features.

These tests are routinely combined by labs to reach a conclusion.

A simple buyer’s checklist

• Certificate issuer: Prefer reports from widely recognised labs such as GIA, AGS or IGI.
• Treatment disclosure: Ensure the certificate clearly states whether the stone has been treated and which method was used.
• Origin statement: Look for explicit wording about whether the colour is natural or laboratory-induced.
• Plotted diagram and comments: A plotted diagram and lab comments add useful detail about inclusions and growth features.
• Ask for recent documentation: Lab techniques improve; a current report reduces the chance that older testing missed treatments.

When specialised testing is needed

Some origin questions require advanced methods and expertise. In difficult or high-value cases, insist on a recent report from a reputable laboratory; detection of subtle treatments or ambiguous origins is a specialist task. Clear, written lab documentation protects buyers and preserves resale value.

Buying and caring for a ring with coloured diamonds

Choosing a coloured-diamond ring combines what looks good with a few practical decisions. Beyond style, attention to colour intensity, cut and protection will keep the stone looking its best for years.

Practical evaluation points

• Colour intensity: The face-up appearance depends on both the cause of the colour and its intensity. Stronger colour intensity usually reads more clearly in ordinary light, so view stones under different lighting conditions.
• Cut considerations: A good cut influences how the colour shows; some cuts concentrate colour, others disperse it. When assessing a stone, look for a balance between brilliance and colour saturation.
• Clarity guidance: For coloured diamonds, inclusions can be less visible when the colour is strong, but clarity still matters. Aim for clarity grades commonly accepted in the trade to ensure an eye-clean appearance and durability.

Setting and protection

• Protective settings: Consider settings that shield the stone from knocks and abrasion. Bezel and partial-bezel styles offer more metal protection around the girdle than delicate prongs, which show off the stone but leave it more exposed.
• Avoid tension settings for coloured diamonds: Tension settings increase the risk of damage or loss and are not recommended for secure long-term wear for coloured diamonds.

Care and maintenance

• Cleaning: Clean coloured diamonds gently with warm water, mild soap and a soft brush to remove oils and dirt. Avoid harsh chemicals and abrasive materials that could dull the metal or affect treated stones.
• Wear precautions: Remove rings during heavy manual tasks, sports or activities likely to expose the stone to impact or rough contact. Careful wear preserves both the diamond and its mounting.
• Professional checks: Have the setting examined periodically by a trusted jeweller to ensure prongs and mounts remain secure and stones are properly seated.

What to ask the seller

• Is there a certificate from a recognised laboratory, and does it state whether the diamond is natural or lab grown? 
• Are any treatments disclosed, and if so, which methods were used?
• Can you see photos or magnified images showing growth zones or inclusions?
• What setting options do you recommend to protect this particular stone?

These questions confirm origin, condition and the most suitable setting for daily use.

Key takeaways

• Prioritise reliable documentation and clear treatment disclosure.
• Choose a setting that balances protection and looks.
• Clean gently, avoid harsh chemicals, and remove the ring for heavy work to maintain brilliance and security.

With these points in mind, a ring set with coloured diamonds can be both a striking style statement and a durable piece of everyday jewellery.