Quick answer: Lab-grown diamonds are created from a diamond seed using one of two primary growth methods: High Pressure High Temperature (HPHT) or Chemical Vapor Deposition (CVD). HPHT uses intense pressure, high temperature, carbon and a metallic growth medium, while CVD uses a low-pressure chamber, carbon-bearing gases and plasma to build diamond layer by layer on a seed.
Once the rough crystal has grown, it still must be inspected, planned, cut, polished and, where applicable, graded before it becomes the finished diamond you see in jewelry.
A polished lab-grown diamond may look effortless, but creating one involves materials science, precision equipment and traditional diamond-cutting craftsmanship. The important point is that a laboratory-grown diamond is not the same thing as a diamond simulant such as cubic zirconia or moissanite.
Laboratory-grown diamonds have the diamond crystal structure and essentially the same fundamental chemical, physical and optical properties associated with diamond. Their growth origin can nevertheless be identified by specialized gemological laboratories using characteristics produced during HPHT or CVD growth.
In this guide, we follow the complete journey from the first diamond seed to a finished gemstone ready to be set into fine jewelry.
What Is a Lab-Grown Diamond?
A lab-grown diamond is a diamond crystal produced in a controlled technological environment rather than extracted from the earth. The two principal commercial production methods are HPHT and CVD.
Both methods supply carbon atoms with conditions that allow them to join an existing diamond seed and extend its crystal structure.
Lab-grown diamonds should not be confused with diamond simulants. Moissanite and cubic zirconia can resemble diamond visually, but they are different materials. A laboratory-grown diamond is made of crystalline carbon arranged in the diamond structure.
If you want a broader introduction before studying the manufacturing process, read our guide on what a lab-grown diamond is .
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How Are Lab-Grown Diamonds Made? The Process at a Glance
Although HPHT and CVD use very different equipment, the complete journey from laboratory growth to jewelry can be simplified into several major stages.
- Prepare a diamond seed.
- Select either HPHT or CVD growth.
- Supply carbon under carefully controlled conditions.
- Allow additional diamond crystal to grow on the seed.
- Remove and inspect the rough crystal.
- Apply post-growth processing when appropriate.
- Plan the rough for maximum useful yield and appearance.
- Cut and facet the diamond.
- Polish the facets.
- Grade or document the finished stone where applicable.
- Match the diamond to a jewelry setting.
- Complete final jewelry inspection and quality control.
Key point: A diamond does not come out of an HPHT press or CVD chamber looking like the polished stone in an engagement ring. The growth stage creates rough diamond material. Cutting and polishing create the final shape, proportions and facet arrangement.
Step 1: Every Lab-Grown Diamond Begins With a Seed
A diamond seed is a small piece of diamond that provides the crystal structure on which new diamond material can grow.
The preparation of the seed matters because the growth process is extending an existing diamond lattice rather than simply transforming a loose pile of carbon into an instantly faceted gemstone.
HPHT and CVD both use diamond seeds, but the seed geometry, growth environment and way carbon reaches the seed differ substantially.
How HPHT Lab-Grown Diamonds Are Made: Step by Step
HPHT stands for High Pressure High Temperature. The process uses extreme pressure and temperature together with a carbon source, diamond seed and metallic growth medium to grow diamond crystal.
Gemological Institute of America research describes typical gem-quality HPHT diamond growth conditions of roughly 5–6 gigapascals (GPa) and approximately 1,300–1,600°C.
HPHT Step 1 — Prepare the Diamond Seed
A small diamond seed is selected and positioned inside the growth assembly. It provides the crystal framework onto which new carbon atoms will attach.
HPHT Step 2 — Add the Carbon Source
A carbon source, commonly graphite, is placed in the growth cell along with the seed.
HPHT Step 3 — Add the Metallic Growth Medium
HPHT diamond growth commonly uses metals such as iron, nickel, cobalt or related alloys as a flux or catalyst system.
Under HPHT conditions, this metallic medium helps transport dissolved carbon toward the growing diamond crystal.
HPHT Step 4 — Place the Growth Cell in the Press
The prepared cell is loaded into specialized high-pressure equipment designed to maintain extremely demanding pressure and temperature conditions.
HPHT Step 5 — Apply Extreme Pressure
Pressure is increased into a range of approximately 5–6 GPa for typical gem-quality HPHT diamond growth.
This is far beyond conditions encountered in ordinary industrial or household environments.
HPHT Step 6 — Raise the Temperature
The growth cell is heated to roughly 1,300–1,600°C.
Under these conditions, the metallic growth medium melts and facilitates movement of carbon through the growth environment.
HPHT Step 7 — Carbon Moves Toward the Seed
A carefully controlled temperature difference encourages carbon to move through the molten metallic medium toward the slightly cooler diamond seed.
HPHT Step 8 — Diamond Crystal Grows
Carbon crystallizes onto the seed in the diamond structure. Continued control of pressure, temperature and chemistry allows the crystal to increase in size.
HPHT Step 9 — Cool and Remove the Rough Diamond
After the desired growth period, the system is brought out of its growth conditions and the resulting rough diamond crystal is recovered.
HPHT Step 10 — Inspect the Crystal
The rough is inspected for growth characteristics, color, inclusions and other features before decisions are made about cutting or further processing.
HPHT-grown diamonds can display growth structures and inclusions related to their production environment. In some material, remnants of metallic flux can become incorporated into the growing diamond.
How CVD Lab-Grown Diamonds Are Made: Step by Step
CVD stands for Chemical Vapor Deposition. Unlike HPHT, CVD diamond growth takes place at relatively low pressure. It uses carbon-containing gas, hydrogen and an energy source to create reactive species that allow diamond to grow on a seed.
CVD Step 1 — Prepare a Thin Diamond Seed
A thin diamond seed or seed plate is prepared with a surface suitable for additional diamond growth.
CVD Step 2 — Place the Seed in the Growth Chamber
The seed is positioned inside a specially designed CVD chamber.
CVD Step 3 — Reduce the Chamber Pressure
The chamber operates at pressures dramatically lower than those used in HPHT. This low-pressure environment is one of the defining differences between the two growth methods.
CVD Step 4 — Introduce Hydrogen and Carbon-Bearing Gas
A gas mixture containing hydrogen and a carbon source—commonly methane—is introduced into the chamber.
CVD Step 5 — Create an Energized Plasma
Energy, commonly microwave energy in commercial systems, activates the gas mixture and produces a plasma.
The plasma contains reactive carbon-bearing species capable of contributing carbon to diamond growth.
CVD Step 6 — Carbon Reaches the Diamond Surface
Carbon-containing species interact with the seed surface. Under appropriately controlled conditions, carbon is incorporated into the diamond lattice rather than simply forming non-diamond carbon.
CVD Step 7 — Diamond Grows Layer by Layer
Additional diamond material gradually accumulates on the seed. This creates the characteristic layered growth associated with CVD production.
CVD Step 8 — Monitor the Growth Cycle
Temperature, gas chemistry, pressure and plasma conditions must remain controlled. The crystal may be grown through multiple stages depending on the equipment, desired dimensions and quality targets.
CVD Step 9 — Remove the Grown Diamond
Once the desired growth has been achieved, the diamond material is removed from the chamber.
CVD Step 10 — Inspect for Color and Growth Features
The resulting CVD material is evaluated for color, strain, inclusions, growth structure and suitability for cutting.
Some CVD-grown material may display brownish coloration or other features that manufacturers choose to modify through post-growth processing. Not every CVD-grown diamond requires the same treatment.
HPHT vs. CVD Lab-Grown Diamonds: What's the Difference?
Both methods can produce gem-quality laboratory-grown diamonds, but they reach that result using fundamentally different growth environments.
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Which Is Better: HPHT or CVD?
Neither HPHT nor CVD is automatically the better choice for every buyer. Both methods are capable of producing attractive, gem-quality laboratory-grown diamonds.
Growth method is only one part of a diamond's story. For a finished gemstone, buyers should pay more attention to the individual stone's appearance, cut quality, color, clarity, carat weight, disclosure of relevant treatment and available grading documentation.
Two diamonds produced by the same method can still look very different after cutting because light performance depends heavily on proportions and facet quality.
Buyer takeaway: Do not reject or select a diamond simply because a listing says “HPHT” or “CVD.” Evaluate the finished diamond as an individual gemstone.
What Happens After a Lab-Grown Diamond Finishes Growing?
Growth is only the beginning. A rough diamond still has to travel through several stages before becoming a polished center stone.
Rough Inspection
Planning
Laser Cutting or Sawing
Bruting and Initial Shaping
Faceting
Polishing
Final Inspection
Grading or Documentation
Jewelry Setting
Specialists examine the grown crystal to understand its usable shape, internal features and possible cutting options.
The rough is analyzed to decide how it can be divided and shaped while balancing carat retention, clarity, proportions and overall value.
Diamond-cutting technology may be used to separate or pre-shape sections of the rough crystal.
The stone begins to receive the outline required for its intended shape, such as round, oval, emerald, pear or another cut.
Individual facets are created at carefully planned angles. This stage strongly influences the finished diamond's interaction with light.
Facet surfaces are polished to achieve the smooth reflective finish associated with a completed diamond.
The polished stone is checked for finish, appearance and other quality factors.
Where an independent laboratory report is supplied, the stone is examined and documented according to that laboratory's current reporting system.
The finished diamond can then be matched with an appropriate setting and secured into the final piece of jewelry.
Explore examples of finished lab-grown diamond engagement rings to see how polished stones are used in complete designs.
Why Are Some Lab-Grown Diamonds Treated After Growth?
Post-growth treatment is used on some laboratory-grown diamonds to modify characteristics such as color. It should not be confused with the actual process that originally grew the diamond.
For example, some CVD-grown diamonds can develop brownish coloration or other growth-related characteristics. HPHT processing may sometimes be used after CVD growth to improve color appearance.
Not every CVD-grown diamond is brown, and not every CVD-grown diamond requires HPHT treatment.
A good grading report or seller disclosure can provide useful information about growth method and relevant post-growth processing where applicable.
Is HPHT-Grown the Same as HPHT-Treated?
No. These terms describe different things.
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A CVD-grown diamond can therefore also be HPHT-treated after its original CVD growth process.
Do Lab-Grown Diamonds Have Inclusions?
Yes. Laboratory-grown diamonds are real growing crystals, so they can contain inclusions and growth features.
Controlled production does not mean every laboratory-grown diamond emerges perfectly flawless.
HPHT-grown material may contain growth features associated with its metallic flux environment, while CVD-grown material can display different growth structures, strain patterns or other characteristics related to layer-by-layer deposition.
These features can also help trained laboratories understand a diamond's growth history.
For a more detailed explanation, read: Growth Lines, Strain and Metallic Inclusions in Lab-Grown Diamonds .
Can a Gemologist Tell Whether a Diamond Is Lab-Grown?
Specialized gemological laboratories can distinguish laboratory-grown diamonds from natural diamonds.
This is an important correction to the common claim that natural and laboratory-grown diamonds are “identical in every testable way.” They share the fundamental properties of diamond, but their different growth environments can produce detectable features.
Laboratories may examine characteristics such as growth morphology, fluorescence behavior, spectral features, inclusions, strain and other indicators using specialized equipment.
A consumer or jeweler looking at a finished stone with the unaided eye generally should not assume that appearance alone is enough to determine origin.
Learn more in our guide: Can a Jeweler Tell If a Diamond Is Lab-Grown by Eye? .
How Are Lab-Grown Diamonds Graded?
After cutting and polishing, a laboratory-grown diamond may be submitted to an independent gemological laboratory for analysis and documentation.
Depending on the laboratory and report type, documentation may include information about:
- laboratory-grown origin;
- growth method;
- carat weight;
- color;
- clarity;
- measurements;
- finish-related characteristics;
- laser inscription or report number where applicable;
- post-growth treatment comments where applicable.
Report formats and grading terminology can change over time, so buyers should read the actual report supplied with the individual diamond rather than assuming every laboratory report contains identical information.
Before buying: If a product is advertised with an independent laboratory report, verify the report number through the issuing laboratory's official verification system when available.
Does Lab-Grown Automatically Mean Sustainable?
No. “Lab-grown” describes a diamond's origin and production route; the term alone does not prove a specific carbon footprint or energy source.
Laboratory-grown diamonds avoid the land excavation required to extract a diamond from a mine. However, HPHT and CVD equipment also consume energy.
The environmental footprint of a particular laboratory-grown diamond can therefore depend on factors such as:
- the growth technology used;
- facility efficiency;
- how long the growth cycle runs;
- the source of electricity;
- post-growth processing;
- cutting and polishing operations;
- transport and other supply-chain factors.
If sustainability is important to your purchase, look for specific, verifiable information about manufacturing and energy sourcing rather than relying on broad phrases such as “eco-friendly” alone.
Are Lab-Grown Diamonds Real Diamonds?
Lab-grown diamonds are diamonds created in a laboratory rather than mined from the earth. They should be clearly described as laboratory-grown, lab-created or another appropriately disclosed term so buyers understand their origin.
They are fundamentally different from diamond simulants such as cubic zirconia and moissanite.
Natural and laboratory-grown diamonds can share the crystal structure, hardness and important optical properties of diamond while still having different origins and identifiable growth characteristics.
How Long Does It Take to Grow a Lab-Grown Diamond?
There is no single growth time that applies to every laboratory-grown diamond.
Growth time depends on factors including:
- HPHT or CVD method;
- equipment design;
- growth rate;
- target crystal dimensions;
- quality requirements;
- number of growth cycles;
- whether interruptions or post-growth processing are required.
Laboratory-grown diamonds are typically produced far more quickly than natural diamonds form within the earth, but consumer claims that promise one universal number of days can oversimplify a process that varies substantially by producer and target stone.
Do Lab-Grown Diamonds Pass a Diamond Tester?
Many conventional diamond testers are designed to identify properties such as thermal or electrical conductivity rather than determine geological origin.
Because laboratory-grown diamonds have diamond's fundamental material properties, a basic tester should not be treated as proof that a stone is naturally mined.
Determining natural versus laboratory-grown origin requires appropriate disclosure, documentation and, when needed, specialized gemological testing.
What Should You Check Before Buying a Lab-Grown Diamond?
Understanding how diamonds are grown is useful, but the individual finished stone matters more than manufacturing terminology alone.
Before purchasing, consider:
- Origin disclosure: The stone should be clearly identified as laboratory-grown or lab-created.
- Cut quality and appearance: A well-cut diamond can make better use of light than a poorly proportioned stone regardless of whether it was grown by HPHT or CVD.
- Color and clarity: Evaluate the actual stone rather than assuming one growth method always produces superior grades.
- Carat weight: Consider dimensions and visual spread as well as the weight number.
- Growth method: HPHT or CVD can be useful background information, but it should not be the only buying criterion.
- Post-growth treatment disclosure: Review the grading report or seller information where relevant.
- Independent report: If a report is advertised, verify the details supplied for that specific stone.
- Setting quality: A high-quality gemstone still needs a secure, appropriately constructed jewelry setting.
- Seller transparency: Ask questions when origin, grading or treatment information is unclear.
If you are deciding whether the category makes sense for your purchase, read our guide on whether buying a lab-grown diamond is worth it .
Design a Ring That Feels Like Your Story
Explore IGI-certified lab-grown diamonds, handcrafted settings, ethical gemstones, and customizable engagement ring designs made for modern love.
Frequently Asked Questions About How Lab-Grown Diamonds Are Made
What are the two main ways lab-grown diamonds are made?
The two primary commercial methods are High Pressure High Temperature (HPHT) and Chemical Vapor Deposition (CVD). HPHT grows diamond under extreme pressure and temperature using a carbon source and metallic growth medium. CVD grows diamond on a seed in a low-pressure chamber using carbon-bearing gas and plasma.
What is a diamond seed?
A diamond seed is a small piece of diamond that provides the crystal structure onto which additional carbon can grow during HPHT or CVD production.
How does the HPHT process make diamonds?
HPHT places a diamond seed, carbon source and metallic growth medium under extremely high pressure and temperatures of roughly 1,300–1,600°C. Carbon is transported through the growth environment and crystallizes onto the seed as diamond.
How does the CVD process make diamonds?
CVD places a diamond seed inside a low-pressure chamber containing hydrogen and carbon-bearing gas such as methane. Energy creates a plasma, allowing carbon species to reach the seed and grow additional diamond material layer by layer.
Which is better, HPHT or CVD?
Neither method is automatically better. Both can produce high-quality diamonds. Buyers should evaluate the individual stone's cut, appearance, color, clarity, carat weight, treatment disclosure and grading information rather than choosing only by growth method.
Can you tell a CVD diamond from an HPHT diamond by looking at it?
Usually not reliably with the unaided eye. Specialized gemological laboratories can identify growth method using equipment and growth-related features that are not necessarily visible to consumers.
Are HPHT diamonds real diamonds?
HPHT-grown diamonds are laboratory-grown diamonds with the diamond crystal structure and fundamental properties associated with diamond. Their laboratory origin should be clearly disclosed.
Are CVD diamonds real diamonds?
CVD-grown diamonds are also laboratory-grown diamonds rather than diamond simulants. They are grown on diamond seeds using carbon-bearing gas in a controlled chamber.
Is HPHT-grown the same as HPHT-treated?
No. HPHT-grown describes the method used to create the diamond crystal. HPHT-treated describes a later process applied to an already-grown diamond to modify characteristics such as color.
Why are some CVD diamonds HPHT-treated?
Some CVD-grown material receives post-growth HPHT processing to modify color or other growth-related characteristics. Not every CVD diamond requires this treatment.
Do lab-grown diamonds have inclusions?
Yes. Laboratory growth is a real crystal-growth process, so inclusions, strain and growth features can occur. Different processes can produce different characteristic features.
Are lab-grown diamonds flawless?
No. Some laboratory-grown diamonds can receive high clarity grades, but being grown in a controlled environment does not guarantee a flawless stone.
How long does it take to grow a lab diamond?
The timeframe varies with the growth method, target crystal size, growth rate, equipment and quality goals. There is no universal number of days that applies to every HPHT or CVD diamond.
What happens after a lab diamond is grown?
The rough diamond is inspected and planned before being cut, shaped, faceted and polished. It may then receive independent laboratory documentation before being matched with a jewelry setting.
Can a jeweler tell if a diamond is lab-grown?
Appearance alone is not a dependable way to determine origin. Specialized testing, reliable documentation and laboratory analysis can distinguish laboratory-grown diamonds from natural diamonds.
Do lab-grown diamonds pass diamond testers?
Basic diamond testers are generally designed around physical properties rather than geological origin, so they should not be used as proof that a diamond was mined. Specialized testing is needed to determine origin reliably.
Are lab-grown diamonds automatically environmentally friendly?
No. They avoid diamond mining, but laboratory growth consumes energy. Environmental impact varies according to production technology, facility efficiency, electricity source and other supply-chain factors.
Does CVD use less energy than HPHT?
Energy use depends on the specific equipment, growth rate, facility and production conditions. A broad claim that every CVD diamond always uses less energy than every HPHT diamond should not be made without production-specific evidence.
Does growth method matter when buying a lab-grown diamond?
It can be useful background information, but for most jewelry buyers the finished diamond's cut, color, clarity, appearance, grading information and disclosure are more useful decision factors than HPHT versus CVD alone.
Final Takeaway: From Carbon to a Finished Diamond
Lab-grown diamond production combines advanced crystal-growth technology with traditional diamond craftsmanship.
HPHT uses extraordinary pressure and temperature to transport carbon to a diamond seed through a metallic growth environment. CVD takes a very different route, using carbon-bearing gases and plasma in a low-pressure chamber to deposit diamond layer by layer.
But neither process ends when the machine stops. The rough crystal still needs inspection, planning, cutting, faceting, polishing and final evaluation before it becomes a finished gemstone.
For buyers, the most important conclusion is simple: growth method tells you how the diamond began; the quality of the individual finished stone tells you what you are actually buying.
Sources & Further Reading
Technical information in this guide has been cross-checked against established gemological and consumer-protection sources. External editorial references open in a new tab and use nofollow in accordance with this site's external-link policy.
- Gemological Institute of America (GIA): HPHT and CVD Diamond Growth Processes — Overview of the two principal laboratory diamond-growth technologies.
- GIA: Observations on HPHT-Grown Synthetic Diamonds — Technical reference for HPHT growth conditions, structure and features.
- GIA: Is There a Difference Between Natural and Laboratory-Grown Diamonds? — Explains why specialized laboratories can distinguish different diamond origins.
- GIA: Laboratory-Grown Diamonds — An Update on Identification and Production — Current research covering HPHT/CVD growth and laboratory identification.
- International Gemological Institute (IGI): Laboratory Grown Diamond Report — Information about IGI laboratory-grown diamond reporting.
- U.S. Federal Trade Commission: Advertising Diamonds, Gemstones and Pearls — Consumer and business guidance on accurate gemstone origin descriptions.
- U.S. Federal Trade Commission: Advertising Diamonds With Clarity — Guidance relevant to laboratory-grown diamond and environmental marketing claims.
Editorial note: This article explains commonly used laboratory-grown diamond production methods using published gemological references. Exact equipment, pressures, temperatures, gas mixtures, growth rates and processing steps can vary by producer and manufacturing system. Product-specific grading, treatment and origin information should be confirmed using the documentation supplied with the individual diamond.