Two very different journeys. Both extraordinary in their own way.
Mined and lab-grown diamonds have very different stories. A mined diamond may have taken billions of years to form deep within the Earth, shaped entirely by Mother Nature. A lab-grown diamond is created using advanced technology; growth time varies by method and target size, but typically ranges from a few days to a few months. Although their origins differ, both are diamonds, sharing essentially the same chemical, physical and optical properties.
At John Macintyre & Son, we love and embrace both. Since 1965, we have helped customers choose diamonds for life’s most important moments. That love of diamonds, together with our knowledge and careful eye for quality, lies behind our long-standing name, The King of Diamonds. We do not believe one origin is right for everyone. Our role is to explain the differences honestly, assess every diamond carefully and help you choose the one that feels right for you.
Watch GIA Explain the Difference
This short film from GIA explains how diamonds formed within the Earth and diamonds grown in a laboratory are created, and how professional gemmological laboratories identify the difference.
Watch the GIA explanation
The Same Diamond Material with a Different Origin
A lab-grown diamond is not an imitation. Mined and lab-grown diamonds are both crystallised carbon arranged in the same cubic crystal structure, with essentially the same chemical, physical and optical properties. Their origin and growth history differ, but the properties that define diamond are shared.
Hardness is one of those shared properties, but it describes resistance to scratching rather than resistance to impact.
What Gives Diamond Its Distinctive Properties
- Composition and colour. Diamond is the only major gemstone composed of a single element: carbon. Trace atoms and crystal defects can influence colour: nitrogen may contribute yellow or brown tones, while boron can produce blue. These are examples; diamond colour has other causes too.
- Crystal form. Mined and lab-grown diamonds share the isometric, or cubic, crystal system. Their rough crystal shapes reflect their growth conditions: natural diamonds commonly form octahedra, HPHT-grown diamonds often show cubic and octahedral faces, and CVD-grown diamonds commonly grow as tabular plates.
Typical examples of rough diamond growth morphology. Individual crystals vary, and origin cannot be determined conclusively from shape alone.
- Light and lustre. Diamond has a refractive index of about 2.42 and dispersion of about 0.044. Together with proportion and finish, these properties contribute to brilliance and fire. Its bright surface sheen is called adamantine lustre.
- Density. Diamond has a specific gravity of about 3.52.
- Birefringence. Diamond is normally singly refractive, though internal strain can produce anomalous birefringence.
- Thermal conductivity. Diamond conducts heat exceptionally well. Thermal testers can distinguish diamonds from many simulants, but they cannot distinguish mined from lab-grown diamonds; moissanite can also give a diamond-like thermal reading. Checking origin requires other screening tests or laboratory analysis.
- Fluorescence. Some diamonds emit visible light under long-wave ultraviolet light, most commonly blue, though other colours occur.
Diamond Anatomy Uses a Shared Industry Language
Mined and lab-grown diamonds are described using the same established diamond-anatomy terminology. The table, crown, girdle, pavilion and culet name the principal parts of a cut diamond, while measurements such as star length and total depth describe aspects of its proportions. These terms describe the diamond’s structure rather than its origin, so they apply equally when discussing GIA-graded mined diamonds and IGI-graded lab-grown diamonds.
GIA established the modern 4Cs framework of cut, colour, clarity and carat weight. Other major gemmological laboratories, including IGI, use the same core diamond-anatomy language, although their diagrams and grading-report formats may present the information differently.
Anatomy of a Round Brilliant diamond. Image courtesy of GIA.
How Mined Diamonds Form
Most mined diamonds formed deep in the Earth’s mantle, commonly around 150–200 km below the surface, where heat and pressure transformed carbon over geological time. Some were carried towards the surface by fast-rising kimberlite or related volcanic eruptions. Their exact growth conditions and carbon sources vary. Each is an ancient creation of Mother Nature, individual in character and almost beyond imagination in age.
How Lab-Grown Diamonds Are Made
Although lab-grown diamonds feel modern, their story began in the 1950s, when scientists first succeeded in producing diamonds in a laboratory, principally for industrial use. It took decades of research and refinement to grow diamonds consistently in the sizes and qualities suited to fine jewellery. As the technology improved and became more widely available, gem-quality lab-grown diamonds became more accessible and grew into an important part of today’s diamond market.
Lab-grown diamonds are produced using two main methods: High Pressure High Temperature (HPHT) and Chemical Vapour Deposition (CVD). Growth time varies by method and target size: HPHT growth may take from about an hour to a few weeks, while CVD growth can range from days to months. The controlled process does not guarantee a particular quality. Colour, inclusions, proportions and cutting quality vary, so the individual diamond and its grading report matter.
Watch IGI explain lab-grown diamonds
HPHT and CVD Growth Processes
The diagrams below show simplified versions of the two main lab-grown diamond growth methods. Conditions vary between stones and producers.
HPHT growth
A temperature gradient carries dissolved carbon through the molten metal flux towards the cooler seed, where it crystallises. The diagram is simplified; equipment and conditions vary.
CVD growth
CVD grows diamond from carbon-containing gas in a low-pressure chamber, without the metal flux used in HPHT. Gas mixtures and operating conditions vary between producers.
Mined and Lab-Grown at a Glance
| Point | Mined diamond | Lab-grown diamond |
|---|
| Origin | Formed within the Earth | Grown in a controlled facility |
|---|
| Timescale | Immense geological time, often billions of years | Varies from about an hour to months, depending on method and size |
|---|
| Material | Diamond | Diamond |
|---|
| Appearance | Can look identical in everyday viewing | Can look identical in everyday viewing |
|---|
| Identification | Confirmed through professional testing and reporting | Confirmed through professional testing and reporting |
|---|
| Price | Generally higher at a comparable specification | Generally lower at a comparable specification |
|---|
| Main appeal | Geological origin, history and finite supply | Modern technology and greater specification flexibility within a price range |
|---|
| Our reports | We specialise in GIA-graded mined diamonds | We use detailed IGI grading reports |
|---|
Quality Still Comes Down to the Individual Diamond
Origin does not decide how beautifully a diamond performs. The 4Cs of cut, colour, clarity and carat weight help describe its quality, but each C answers a different question.
- Cut describes how well a diamond has been proportioned and finished. It has a major influence on brightness, fire and scintillation.
- Colour describes how colourless a diamond appears within the relevant grading scale.
- Clarity records internal and external features examined under controlled conditions and magnification.
- Carat is a measure of weight, not a guarantee of visible size or beauty.
Two diamonds with the same carat weight can look very different. Measurements, proportions, shape, cut quality and the way the stone handles light all affect its appearance. This is why we assess more than the number on the label.
Why We Use GIA for Mined Diamonds and IGI for Lab-Grown Diamonds
Independent grading has always been central to how we sell diamonds. It is the principle behind our Honest Diamond Grading campaign: customers should be able to see an impartial record of a diamond’s identity and quality rather than rely on a retailer’s description alone. For mined diamonds, we have long championed GIA. GIA created the 4Cs framework used throughout the industry, and its Diamond Grading Report provides an independent assessment of the stone’s quality characteristics.
As lab-grown diamonds became an increasingly important part of the market, we wanted to bring the same philosophy to our lab-grown diamond collection. IGI pioneered lab-grown diamond grading in 2005 and is one of the field’s leading laboratories. Its Laboratory Grown Diamond Report identifies the stone as lab-grown and records the detailed 4Cs information we want our customers to see, together with measurements, finish and other relevant details. That specialist history and report detail are why we pair our carefully selected lab-grown diamonds with IGI grading.
The GIA-graded mined diamonds and IGI-graded lab-grown diamonds we offer are laser-inscribed on the girdle with the number corresponding to their independent gemmological grading report. For mined diamonds, this is the GIA Diamond Grading Report; for lab-grown diamonds, it is the IGI Laboratory Grown Diamond Report. The inscription is microscopic and is normally viewed under magnification. Although 10x magnification may be sufficient, at John Macintyre & Son we often use 20x magnification to make the inscription easier to see, helping the diamond to be matched with its report and verified online.
Customers can independently confirm report details using GIA Report Check or IGI Verify Your Report.
Matching an Inscription to an IGI Report
Here is an example using one of our lab-grown oval diamonds, in stock when this report was prepared. The IGI Laboratory-Grown Diamond Report describes an Oval Brilliant weighing 1.82 ct, graded D colour and VVS2 clarity, with Excellent polish and symmetry and no fluorescence. The loose diamond is shown beside a magnified sample image of its girdle inscription. The inscription number LG732553420 matches the IGI report number. The report also records CVD growth and Type IIa. Availability may change.
The loose oval in tweezers beside the magnified inscription image associated with its IGI report.
IGI Laboratory-Grown Diamond Report for the same oval. Report photograph supplied by John Macintyre & Son.
Open IGI Verify Your Report and enter report number LG732553420.
Watch IGI explain its role in lab-grown diamond grading
Watch GIA explain how to read a GIA Diamond Grading Report
Grading laboratories do not all present lab-grown results in the same way. IGI continues to use detailed 4Cs reporting for lab-grown diamonds. On 2 June 2025, GIA announced that it would replace the colour and clarity nomenclature previously used for lab-grown diamonds, which was originally developed for mined diamonds, with a two-tier quality assessment. The revised service launched on 1 October 2025 and classifies qualifying colourless-to-near-colourless lab-grown diamonds as Premium or Standard. A submitted diamond that does not meet all of GIA’s minimum criteria for Standard does not receive a GIA assessment. The formats should therefore be read on their own terms rather than compared as if they were identical.
GIA Laboratory-Grown Diamond Quality Assessment example showing a Premium result. Image courtesy of GIA; shown for education and not as a report for a diamond offered by John Macintyre & Son.
Two Diamonds Two Origins Comparable Specifications
These loose round brilliant diamonds show how two stones with a similar colour, clarity and fluorescence profile can have different origins. Both are E colour, Internally Flawless and have no fluorescence. The mined diamond is graded by GIA; the lab-grown diamond is graded by IGI. Their reports should be read using each laboratory’s own grading terms.
| Specification | Mined diamond | Lab-grown diamond |
|---|
| Origin | Mined | Lab-grown |
|---|
| Shape and cutting style | Round Brilliant | Round Brilliant |
|---|
| Carat weight | 1.01 ct | 1.02 ct |
|---|
| Measurements | 6.46–6.51 × 3.92 mm | 6.50 × 6.52 × 3.89 mm |
|---|
| Colour | E | E |
|---|
| Clarity | Internally Flawless (IF) | Internally Flawless (IF) |
|---|
| Fluorescence | None | None |
|---|
| Cut grade | Excellent | Ideal |
|---|
| Polish | Excellent | Excellent |
|---|
| Symmetry | Excellent | Excellent |
|---|
| Table | 59% | 59% |
|---|
| Total depth | 60.4% | 59.7% |
|---|
The GIA report describes the mined diamond as Excellent cut, Excellent polish and Excellent symmetry, often called Triple Excellent. The IGI report describes the lab-grown diamond as Ideal cut, Excellent polish and Excellent symmetry. The laboratories use different grading systems, so their cut labels should not be treated as interchangeable.
IGI-graded lab-grown diamond
GIA-graded mined diamond
These separately recorded videos show two individually graded round brilliant diamonds with closely matched specifications: one mined and GIA-graded, the other lab-grown and IGI-graded. They illustrate how similar the two origins can appear, while professional testing and the accompanying grading report provide reliable identification.
Price and What Your Budget Can Achieve
Lab-grown diamonds generally cost less than mined diamonds with broadly comparable specifications. The price difference often becomes more noticeable as carat weight increases, particularly above 1.00 carat. A fair comparison should consider the same shape, carat weight, colour, clarity, cut or proportions, polish, symmetry, fluorescence and, for elongated shapes, length-to-width ratio.
For many of our customers, this creates more freedom to choose a higher colour or clarity grade, a larger centre stone, diamond-set shoulders, or a platinum or 18ct gold setting. With precious-metal prices remaining high, lab-grown diamonds have also helped us offer a wider choice of rings below £2,000.
A mined diamond’s price reflects a different supply journey, including exploration, recovery and sorting, as well as the relative scarcity of particular combinations of size and quality. Customers may value its geological origin, age and established place in jewellery tradition.
We do not publish a fixed percentage saving because diamond prices change and fair comparisons must include the complete diamond specification, report, metal and setting. A very large diamond is not automatically the best diamond for your ring. Whether you choose mined or lab-grown, we aim to provide exceptional quality at an exceptional price.
Value and Resale
We believe a diamond ring should be chosen for beauty, meaning and suitability rather than a promised investment return. Mined diamonds have a longer-established secondary market, while lab-grown prices have changed quickly as production has expanded. Neither origin should be sold with a guarantee that it will rise in value, and jewellery commonly resells for less than its original retail price. Our focus is the value you receive when you buy: a carefully selected diamond, a high specification and a highly competitive price. We believe that is a more honest measure of value than making promises about what any diamond may be worth in the future.
Environmental and Social Considerations
We believe there is no responsible basis for saying that every lab-grown diamond is automatically sustainable or that every mined diamond has the same impact. The answer depends on the producer, energy source, mine, working practices, traceability and wider supply chain.
Diamond mining changes land and uses resources, but well-managed diamond industries can also support employment, local businesses and public revenue. Botswana is an important example of a country where diamond income has played a central role in national development. Those benefits depend on governance and how revenue is invested; they cannot be assumed for every diamond or every producing country.
Lab-grown production avoids mining the centre stone, but it requires substantial energy. Its footprint can vary greatly depending on how efficiently the facility operates and whether its electricity comes from renewable or fossil-fuel sources. Any specific environmental claim should be supported by evidence for that producer rather than applied to the whole category.
A grading report documents identity and quality characteristics. It does not, by itself, prove every ethical, environmental or labour claim about a diamond’s full supply chain.
The setting also has an environmental footprint. Gold and platinum are mined materials, whether the centre diamond is mined or lab-grown. Recycled precious metals can reduce demand for newly mined material, but no ring should be described as impact-free without evidence covering the full supply chain.
A Note on the Words Used
You may see the terms lab-grown diamond, laboratory-created diamond or synthetic diamond. In gemmology, synthetic describes a material made by people with essentially the same chemical and physical properties as its mined counterpart. It does not mean cubic zirconia, moissanite or a fake diamond.
Terminology differs between countries and industry organisations, and it continues to evolve. We use lab-grown diamond because it is clear, familiar to our customers and consistent with the wording we use in-store and online. Whatever term is used, the origin should always be disclosed prominently.
Which Diamond Is Right for You
There is no universal winner. The best choice is the diamond that suits the wearer, the ring and the priorities behind the purchase. Sometimes the decision comes down to price range: after comparing the available options, you may find that either a mined or lab-grown diamond is the better fit. These questions can help you decide.
- Has the person wearing the ring expressed a preference for a mined or lab-grown diamond?
- Does geological origin and history carry particular meaning for you?
- Would you prefer to use more of the budget for a particular carat weight or quality specification?
- Are you comparing complete specifications, measurements and reports rather than carat weight alone?
- Have you seen the diamond clearly in person or on video, and do its shape, measurements and proportions suit your chosen setting?
Choose in Glasgow or From Further Afield
At our appointment-based Glasgow showroom, we hold a carefully chosen selection of sample engagement rings so you can try different designs, diamond shapes and settings. You will be guided by one of our five specialists, each with more than 20 years’ experience helping customers choose diamonds and engagement rings. Most of our rings are made to order, with the centre diamond and mount selected separately around your preferred diamond origin, shape, carat weight, quality, precious metal and budget. This gives you a much wider choice than limiting you to ready-made rings in a display cabinet. It can also help you achieve a higher diamond specification or carat weight at a highly competitive price. Where suitable examples are available, we can compare mined and lab-grown diamonds and talk you through their grading reports before creating the ring that is right for you.
Our appointment-based Glasgow showroom on Mitchell Lane.
If you are further afield, we offer the same personal guidance by telephone, email or WhatsApp. When possible, we will share the independent grading report, clear photographs and a video of the loose centre diamond before approval, so you can consider the individual stone and its specification wherever you are.
Frequently Asked Questions
Are lab-grown diamonds real diamonds?
Yes. They are diamonds with essentially the same chemical, physical and optical properties as mined diamonds. Their defining difference is that they are grown in a controlled environment rather than formed within the Earth.
Are they the same as cubic zirconia or moissanite?
No. Cubic zirconia and moissanite are different materials used as diamond simulants. A lab-grown diamond is crystallised carbon and is identified as diamond.
Can you tell the difference by looking?
Not reliably by eye. Mined and lab-grown diamonds have essentially the same chemical, physical and optical properties, so they can look the same in normal viewing. Their different growth environments can produce diagnostic growth patterns and other features, but these vary from stone to stone. Gemmological laboratories use specialist instruments and a combination of tests to determine origin.
Do lab-grown diamonds sparkle differently?
Origin does not decide sparkle. Cut quality, proportions, polish, symmetry and the individual stone determine how it handles light.
Are all lab-grown diamonds flawless?
No. Lab-grown diamonds can have inclusions, colour and growth features, and they vary in cut quality. Each diamond should be assessed individually.
Will either type hold its value?
Future value cannot be guaranteed. Mined diamonds have a more established secondary market, while lab-grown prices have moved quickly as supply has increased. We recommend choosing for beauty, meaning and suitability rather than investment. Our focus is what we can control: careful selection, high specifications and highly competitive pricing, so you receive exceptional quality at an exceptional price from the outset.
Which is best for an engagement ring?
Both are durable diamonds suitable for everyday jewellery. The right choice depends on the intended wearer’s preference, the meaning you attach to origin, your price range and the specification you want.
Can I choose a diamond without visiting the showroom?
Yes. We can help by telephone, email or WhatsApp. When possible, we will share the diamond certificate together with clear photographs and a video of the loose centre diamond before approval.
Ready to Compare Mined and Lab-Grown Diamonds?
Tell us what matters most to you, and we’ll help you compare suitable diamonds, review their grading reports and choose the one that feels right. Visit our Glasgow showroom by appointment, or contact us by phone, email or WhatsApp if you’re further afield.
Make an Engagement Ring Enquiry
