A gemstone can partially absorb visible light. To study that phenomenon, the specialists use a visual spectrophotometer. This device shines a narrow ray of visible light through the stone: from light with the lowest frequency (longest wavelength) that we as people can still see as red light, to light with the highest frequency (shortest wavelength), which we see as violet light. Light with certain frequencies (and certain colours), is absorbed less, and thus escapes from the diamond. This escaping light determines which colour the diamond appears to be.

The spectrophotometer captures the emerging light. The end result is a graph that reflects either the radiated or the absorbed light per wavelength. By studying that graph, the expert discovers among others, where the colour of a diamond originates from.

Buyer takeaway: Detects subtle colour origins by measuring which visible wavelengths a diamond absorbs. For buyers this means labs can distinguish natural tints from unusual colour causes; ask the seller for the lab's colour grade and any spectral notes when colour is important for your purchase.

A gemstone also absorbs infrared light. We cannot perceive that light with the naked eye, we feel it as heat instead. The stone can absorb, transmit or reflect the infrared light.

In order to map this phenomenon, for example, the expert exposes a diamond to an infrared spectrophotometer. It emits light with different infrared frequencies or wavelengths. This is how the researcher can find out which type of diamond he or she is analysing. A Type I diamond gets its colour from chemical impurities, whilst a Type II diamond get its colour from structural deviations in the crystal form. 

At the same time the specialist discovers whether a coloured gemstone has been treated with substances such as resin and oil. This malicious technique is used to improve the gloss. But the research method with infrared light also helps to, for example, discover diamonds that have been irradiated to improve their colour.

Buyer takeaway: Reveals chemical impurities and structural types that explain colour and flag certain treatments. If you are considering a coloured or high‑value stone, request IR screening results or a recognized lab report that comments on treatment indicators.

With a Raman-spectrometer the specialist shines a laser light of almost one single colour onto a certain material. Most of the light does not change colour, or change wavelength. But a small part of the light wavelength does change. The exact extent of this varies from molecule to molecule. According to the strength of the effect, molecules can be identified. In other words …

By comparing the light emitted with values of other materials that were previously examined with a Raman spectrometer, the expert can find out perfectly which material they are examining. For example, a diamond.

Buyer takeaway: Provides a molecular fingerprint to confirm whether the material is a diamond or another substance. Insist on an independent lab confirmation for valuable pieces so you know you are buying a genuine diamond rather than an imitation.

A mouthful, isn’t it? With this device, the expert examines the crystal structure of a precious stone. For this purpose, a sample of it is ground into powder (if this is possible, of course) and then exposed to X-rays. These rays are broken or bent at certain angles, depending on the atomic structure of the crystal.

By comparing the pattern by which the X-rays differ with patterns that were previously determined by different types of precious stones, the specialist knows exactly which type of gemstone lies in front of them and ends up in your diamond necklace later on. For this the expert has to sacrifice a small sample of the stone.

Buyer takeaway: Maps crystal structure to identify natural versus some synthetic forms, though sampling may be needed. For rare or exceptional stones, ask whether any destructive testing was performed and request documentation of the findings.

Again not a simple term, we know. But the science behind it allows an expert to very quickly discover the chemical elements of a gemstone, albeit without knowing the exact proportions. And that without the researcher having to sacrifice part of the stone.

As with the diffractometer above, the expert irradiates a gemstone with X-rays. The material itself then emits other X-rays, which are typical of the chemical elements of which the diamond is composed. We call this phenomenon X-ray fluorescence. This is a variation on ordinary fluorescence, a phenomenon where a substance emits light when it is illuminated. An example of this? Just think of the fluorescent vest in your car.

Buyer takeaway: Quickly identifies the chemical elements present and helps spot treatments without damaging the stone. Buyers should prefer non‑destructive screening results on the certificate, especially when provenance or treatment history matters.

Want to know how a specialist knows the proportions of chemical elements in a gemstone? He or she can determine this with an LA-ICP mass spectrometer. This device focuses a laser beam on a sample of the precious stone, removing small particles. These are then taken by a running gas to a so-called plasma torch.

The torch heats these particles in such a way that they completely disintegrate into their individual atoms. This allows the researcher to accurately map every quantity of each chemical element of the gemstone, down to the lowest concentrations. An amazing result, and only a very limited amount of diamond is lost.

Both the research of the X-ray fluorescence and the LA-ICP mass spectrometer allow you to check whether the diamond that ends up in your diamond necklace or ring, is natural or synthetic, or if it has been treated.

Buyer takeaway: Measures trace elements with great precision, supporting detection of treatments and sometimes origin claims. This level of testing is most relevant for investment or collector purchases; ask for trace‑element reports when provenance is a deciding factor.

A final series of devices provides the expert with extreme close-up photos of certain characteristics or inclusions in a gemstone. This allows the scientist to discover how the material has formed and, in certain cases, even where the stone comes from.

With a photo-microscope for example, photographs taken of inclusions and other aspects of gemstones are enlarged one hundred times.

In addition, the diamond producer De Beers developed the DiamondView-instrument, a device to distinguish synthetic from natural diamonds. This device shines ultraviolet light on the gemstone, after which it fluoresces.

Depending on whether the diamond was created by the forces of mother nature or in the lab, the colour of the fluorescence and its pattern differ. With a synthetic diamond there is no phosphorescence, unlike its natural counterpart. Phosphorescence is a phenomenon in which the gemstone, after being exposed to light, shortly lights up afterwards itself.

Buyer takeaway: Provides inclusion photos, growth pattern images and fluorescence data that visually support grading and origin conclusions. Always request any inclusion maps or imaging plates for significant purchases so the stone's characteristics are documented for resale and insurance.

Fracture filling - what it is: small surface‑reaching cracks are filled with a glassy substance to mask breaks and improve apparent clarity. How it affects appearance/value: treated stones can look clearer at a glance but typically have lower market value and must be disclosed. Which instruments detect it: visible under magnification and often flagged by Raman or infrared signatures and by inclusion photos.

HPHT (high pressure, high temperature) - what it is: a laboratory process that can change a diamond's colour, making it whiter or producing fancy colours in some cases. How it affects appearance/value: HPHT can change colour significantly and therefore affects market value; full disclosure is required. Which instruments detect it: infrared screening and DiamondView imaging commonly reveal HPHT indicators; LA‑ICP‑MS and trace‑element tests provide supporting evidence.

Irradiation - what it is: exposure to radiation to alter or intensify colour. How it affects appearance/value: irradiation can produce vivid colours or modify body colour but treated stones are disclosed and priced differently from naturally coloured diamonds. Which instruments detect it: infrared and photoluminescence tools, plus specialized imaging, can reveal irradiation markers.

Coating - what it is: a thin surface layer applied to change apparent colour or gloss. How it affects appearance/value: coatings can be temporary and are removable; coated stones are treated and have reduced market value. Which instruments detect it: visible inspection with magnification, XRF for surface elements, and spectrophotometry often reveal coatings.

Note: grading of the 4Cs and disclosure practices remain the responsibility of grading laboratories; always request the lab report and any treatment comments before purchase.

In addition to high-tech devices as discussed above, diamond specialists also use some 'simpler' devices. For example, a magnifying glass or a microscope, but also a polariscope. With the latter device the specialist can distinguish gems by how the light is broken, either once or twice. The first type includes diamonds. Emerald, ruby and sapphire are part of the second category.

Laboratory instruments do more than satisfy a scientist's curiosity; their findings directly affect authenticity statements, certificate comments and ultimately the market value of a stone. For a buyer, the important point is not the name of the machine but what its result says on a lab report and what that means for resale, insurance and long‑term confidence.

Visual spectrophotometer - plain language

What it detects: how the diamond absorbs and transmits visible light, explaining subtle body colour and tint. How it appears on a report: a lab comment may note specific absorption bands or a measured colour range. Buyer implication: slight natural colour deviations detected by this method can affect the colour grade and therefore price; ask for the lab colour grade if appearance is a major factor in your choice.

Infrared spectrophotometer - plain language

What it detects: chemical impurities and structural types that explain why a diamond has colour or if treatments are present. How it appears on a report: a type designation or a note when treatment indicators are found. Buyer implication: infrared results help separate naturally coloured stones from those altered by treatment or irradiation, which matters for both value and disclosure when reselling or insuring.

Raman spectrometer - plain language

What it detects: the material's molecular fingerprint, used to confirm whether the stone is genuine diamond or another material. How it appears on a report: confirmation of diamond identity or a flag if a non‑diamond substance is identified. Buyer implication: a Raman confirmation reduces the risk of misidentification; insist on a recognized lab report for high‑value purchases.

X‑ray diffractometer (XRD) - plain language

What it detects: the crystal structure, which can identify natural versus some synthetic crystal forms. How it appears on a report: structural identification or a note when testing required a sample. Buyer implication: because XRD can require sampling, its findings are usually detailed in specialist reports; for rare or valuable stones, ask whether any sampling took place and request the results in writing.

X‑ray fluorescence (XRF) - plain language

What it detects: which chemical elements are present at the stone's surface or near‑surface, useful to flag certain treatments or unusual trace elements. How it appears on a report: elemental signatures or a statement that XRF screening was performed. Buyer implication: XRF helps labs detect treatments without damaging the stone, which supports confident valuation and clearer insurance listings.

LA‑ICP‑MS - plain language

What it detects: precise trace‑element composition down to very low concentrations, which can identify treatments and sometimes point to geographic origin. How it appears on a report: detailed trace‑element data or a reference to provenance testing. Buyer implication: trace‑element profiles add strong scientific support to claims about origin or treatment; they are especially relevant for collectors and investment buyers seeking provenance-backed pieces.

Imaging (photo‑microscope, DiamondView) - plain language

What it detects: inclusions, growth patterns and fluorescence behaviour that reveal natural formation versus lab growth or treatments. How it appears on a report: photographic plates, inclusion maps or fluorescence descriptions. Buyer implication: clear imaging supports grading decisions and helps future buyers visually verify the stone; request any inclusion photos or DiamondView notes when considering an important purchase.

Quick checklist for buyers

• For routine purchases at typical retail levels, make sure the diamond carries a current report from a reputable lab that lists the 4Cs and notes any treatments.
• For higher‑value or investment purchases, ask whether the lab performed infrared, Raman or LA‑ICP‑MS screening and request any inclusion photography or provenance notes.
• If a certificate mentions treatment indicators, obtain full disclosure and consider how that affects resale and insurance.
• When in doubt, request a written lab comment rather than a verbal assurance from a seller; documented instrument results give the clearest protection for future value.