Natural, Treated or Lab-Grown? What Trade Buyers Should Know

By the Byrex Gems team, Toronto · Published 25 September 2026

How laboratory-grown diamonds and gems are made, which treatments are common, how leading laboratories detect them, what disclosure rules require, and why natural untreated stones hold value.

Three stones can look almost identical across a counter: one formed in the earth and left as found, one natural but treated to improve its colour or clarity, and one grown in a laboratory. Their values can differ enormously. For trade buyers, knowing which is which, and how that knowledge is documented and disclosed, is fundamental. This guide sets out how laboratory-grown stones are made, which treatments are common, how the leading laboratories detect them, what the disclosure rules say and what recent market data says about price.

How laboratory-grown diamonds are made

Laboratory-grown diamonds are real diamonds, not imitations. The US Federal Trade Commission recognised in 2018 that they share essentially the same optical, physical and chemical properties as mined diamonds. Two production methods dominate.

HPHT (high pressure, high temperature)

HPHT growth recreates the crushing pressure and heat of the Earth's mantle inside a press, using carefully chosen starting materials to promote crystal growth. According to GIA, General Electric produced the first commercially available synthetic diamonds by this route in 1956, initially for industrial use.

CVD (chemical vapour deposition)

CVD works the other way round, at very low pressure. A mixture of a hydrocarbon gas, usually methane, and hydrogen is energised in a vacuum chamber, typically with microwaves, so that carbon atoms settle layer by layer onto a diamond seed plate at roughly 900 to 1,200 °C. GIA notes that scientists learned to grow diamond reproducibly by CVD in the late 1980s. Today CVD and HPHT material are both widely used in jewellery.

How laboratory-grown coloured stones are made

Synthetic coloured stones have a much longer history. A 2024 review in GIA's Gems & Gemology describes four main methods:

Flame fusion (Verneuil). Fine alumina powder with a colouring agent such as chromium oxide is melted through an oxygen-hydrogen flame and builds up as a boule on a slowly lowered pedestal. Verneuil perfected the method in the late nineteenth century and published it in 1904. It is used for synthetic ruby, sapphire and spinel, among others.
Flux growth. Crystals grow slowly from a molten chemical solvent. The technique was developed between the 1920s and 1940s and became commercially significant in the 1970s for ruby, emerald, alexandrite, sapphire and spinel. Because it is slow and costly, it is now less common.
Hydrothermal growth. Crystals grow from hot, pressurised water-based solutions, the method closest to the way many gems form in nature. It is used for quartz, emerald, ruby, sapphire and spinel.
Crystal pulling (Czochralski). A rotating seed is drawn slowly from a melt. Dating from 1918, it is used for corundum, alexandrite and spinel, among others.

Common treatments of natural diamonds

A treated stone is still natural, but its appearance has been altered after mining. For diamonds, the treatments that matter most to trade buyers are:

HPHT colour change. In March 1999 General Electric and Lazare Kaplan announced a permanent process that used high pressure and temperature to remove brown colour from certain natural diamonds, producing stones graded in the D to G range. GIA had documented more than 2,000 such stones by late 2000, and the process was later adapted to produce pink, blue and yellow colours. The stones most suited to decolourisation belong to the rare type IIa group, which SSEF estimates at about three percent of natural diamonds.
Irradiation and annealing. Exposure to radiation, often followed by controlled heating, can create a wide range of colours, from green and blue to pink, red and purple. GIA describes irradiation as frequent in fancy colour diamonds.
Coating. Thin surface films, some applied by sputtering, can add a pink or other tint. Coatings are vulnerable to scratching, especially along facet edges.
Fracture filling. Glass-like fillers can make surface-reaching fractures less visible.

Common treatments of coloured gemstones

Heat. GIA describes heating of ruby and sapphire as extremely common. It can intensify blue in sapphire or remove purplish tints from ruby, and the results are considered stable under normal wear. For some other gems, including aquamarine, citrine, amethyst and tourmaline, heating is usually undetectable, and GIA's researchers have advised assuming that most such material has been heated.
Beryllium diffusion. In early 2002 it emerged that many orange and pinkish-orange sapphires on the market owed their colour to beryllium diffused into the stone at high temperature. The treatment can penetrate the entire stone and alter almost any corundum colour, and its reliable detection required chemical analysis by mass spectrometry that gem laboratories did not initially have.
Lead-glass filling. From around 2004, heavily fractured, low-grade corundum began to be filled with high-lead glass, turning otherwise non-gem material into transparent stones. The glass is vulnerable to acids and shows characteristic blue and orange flashes under magnification.
Emerald fillers. Filling surface-reaching fractures in emerald with oils or resins is a long-standing practice, and the merits of traditional oils versus polymers have been debated since the 1990s. Because the type and amount of filler matter to value and durability, laboratories describe the degree of clarity enhancement on their reports.

How laboratories detect synthetics and treatments

Many of these distinctions cannot be made with a loupe. They depend on spectroscopy, trace-element chemistry and the study of inclusions, backed by large reference collections.

GIA has changed how it documents laboratory-grown diamonds. Since 1 October 2025, its reports for laboratory-grown diamonds no longer use the D-to-Z colour scale or the natural clarity grades. Instead they describe each stone as Premium or Standard, and the girdle is laser-inscribed "Laboratory-Grown" with the report number. GIA explained that most laboratory-grown diamonds fall into a very narrow quality range.

SSEF, the Swiss Gemmological Institute, announced in April 2000 that it could detect HPHT treatment in type II diamonds, relying mainly on photoluminescence spectroscopy at low temperature. An independent blind test by De Beers' research unit in May 2000 confirmed the result. SSEF is also known for its work on important coloured stones: when it examined the 55.22-carat Estrela de Fura ruby, it found no indications of heating, citing a mineral inclusion that would not have survived heat treatment.

GRS (GemResearch Swisslab) operates six laboratories across Europe, Asia and the United States and specialises in origin determination and treatment detection for ruby, sapphire and emerald, as well as spinel, tourmaline and garnet.

For trade buyers, the practical lesson is that the report matters as much as the stone. A report from a recognised laboratory should state whether a diamond is natural or laboratory-grown, whether its colour is natural, and for coloured stones whether there is evidence of heating or other treatment and, where relevant, the degree of clarity enhancement.

What the disclosure rules say

United States: FTC Jewelry Guides (2018)

On 24 July 2018 the FTC approved revisions to its Guides for the Jewelry, Precious Metals, and Pewter Industries. The key points for gemstones are:

The word "natural" was removed from the definition of diamond, reflecting that laboratory-grown diamonds are diamond.
Laboratory-grown diamonds may be called "cultured" only if the term is immediately accompanied, with equal prominence, by a qualifier such as "laboratory-grown", "laboratory-created" or "[manufacturer name]-created".
The FTC stopped recommending "synthetic" for laboratory-grown diamonds because of the risk of consumer confusion, but did not ban it, provided it is not used to imply that a competitor's product is not diamond.
Lead-glass-filled stones should be described with terms such as "composite", "hybrid" or "manufactured", and misleading varietal names are not acceptable.

Separately, section 23.24 of the Guides calls on sellers at every level of the supply chain to disclose a gemstone treatment if it is not permanent, if it creates special care requirements, or if it significantly affects value. Disclosure should be made at or before the point of sale, including in online listings.

Canada

In Canada, misleading representations are governed by the Competition Act and enforced by the Competition Bureau. The Canadian Jewellers Association's guidelines on advertising laboratory-grown diamonds draw on that framework and on the FTC Guides. They call for "synthetic", "laboratory grown" or "lab created" to appear immediately before the word "diamond", with neither part given greater prominence and without separating the terms.

International: the CIBJO Blue Books

CIBJO, the World Jewellery Confederation, publishes seven Blue Books covering diamonds, coloured gemstones, pearls, coral, precious metals, gemmological laboratories and responsible sourcing. They set out grading standards and nomenclature, are reviewed annually for revision or reaffirmation, and can be downloaded free from CIBJO's website.

What has happened to laboratory-grown prices

Laboratory-grown diamond prices have fallen steeply as production has expanded. When De Beers launched its Lightbox brand in 2018, it priced laboratory-grown stones at US$800 per carat. On 8 May 2025 De Beers announced it intended to close Lightbox, stating that wholesale prices for laboratory-grown diamonds in jewellery had fallen by 90 percent since the brand's launch. De Beers said its Element Six subsidiary would focus on industrial and technology applications of synthetic diamond.

Independent analysis tells a similar story. Industry analyst Edahn Golan reported a further 14 percent fall in laboratory-grown wholesale prices in the first quarter of 2026, with three-carat rounds down 28 percent and one-carat rounds down 15 percent year on year. His second-quarter report, published in July 2026, showed a further 13 percent annual decline and a cumulative fall of about 96 percent since he began tracking prices in July 2018.

Natural fancy colour diamonds have behaved very differently. The Fancy Color Research Foundation's index, which tracks yellow, pink and blue diamonds, slipped just 0.1 percent in the second quarter of 2026 and 0.5 percent over twelve months.

Why natural, untreated stones command a premium

The premium for natural, untreated stones rests on a few straightforward points:

Scarcity cannot be manufactured. Laboratory output can expand with demand and technology, and competition among producers has driven prices down. The supply of natural stones of fine colour is finite.
Untreated stones are scarce. Where heating is extremely common, as GIA says it is for ruby and sapphire, stones with no evidence of heating are correspondingly rare. GIA notes that treated stones are worth less than comparable untreated ones.
Permanence and care. Some treatments, such as coatings, oils and lead glass, can be damaged in wear or at the bench. Untreated stones carry no such caveats.
Documented results. Records such as the US$34.8 million paid at Sotheby's New York in June 2023 for the Estrela de Fura, a ruby that SSEF found to show no indications of heating, illustrate how the market rewards stones that are both natural and untreated.

A short checklist for trade buyers

Ask for a current report from a recognised laboratory, and check the report number online where the laboratory offers verification.
Confirm in writing whether the stone is natural or laboratory-grown, and whether its colour is natural.
For coloured stones, read the treatment section carefully: "no indications of heating", "heated" and the degree of any clarity enhancement all affect value.
Pass the same disclosure on to your own customers, in line with the FTC Guides in the United States and the Competition Act in Canada.

If you would like to discuss natural fancy colour diamonds or coloured gemstones with laboratory reports, please email info@byrex.com or send a WhatsApp message to +1 (437) 450-3786.