How Are Lab Grown Diamonds Made? CVD vs HPHT Explained (2026)

Lab grown diamonds are real diamonds — chemically and physically identical to mined diamonds — produced in controlled laboratory environments using two scientifically validated methods: HPHT (High Pressure High Temperature) and CVD (Chemical Vapor Deposition). Both methods produce stones with the exact same crystal structure, hardness, and brilliance as natural diamonds. This guide explains exactly how each method works, what the differences are between CVD and HPHT diamonds, how long the process takes, and what to look for when choosing a lab grown diamond produced by either method.

Last updated: April 2026 by the Mohana Jewels editorial team.

The two ways lab grown diamonds are made

Every lab grown diamond on the market today is produced using one of two methods. Both methods recreate the conditions under which natural diamonds form in the earth's mantle, but they take fundamentally different approaches:

• HPHT (High Pressure High Temperature): Recreates the extreme conditions deep within the earth where natural diamonds form. Developed in the 1950s, this is the older and more energy-intensive of the two methods.
• CVD (Chemical Vapor Deposition): Builds a diamond crystal atom by atom from carbon-rich gas. Developed in the 1980s and refined dramatically in the 2010s, CVD has become the dominant production method for gem-quality lab grown diamonds.

Both methods produce real diamonds — pure carbon arranged in the diamond crystal structure. The Federal Trade Commission, GIA, IGI, and every major gemological authority recognize lab grown diamonds from both methods as real diamonds. Read our complete guide to what lab grown diamonds are.

Method 1: HPHT (High Pressure High Temperature)

HPHT was the first commercially successful method for growing diamonds. It works by replicating — at industrial scale — the conditions that create natural diamonds deep in the earth's mantle.

The HPHT process step by step

1. A diamond seed crystal is placed inside a specialized growth chamber. The seed acts as the foundation onto which the new diamond grows.
2. Carbon source material is added. This is typically high-purity graphite — the same form of carbon found in pencil lead — along with a metal catalyst (commonly iron, cobalt, or nickel).
3. The chamber is sealed and subjected to extreme conditions. Pressure rises to approximately 5-6 GPa (gigapascals) — roughly 50,000 times atmospheric pressure. Temperature climbs to 1,300-1,600°C.
4. The carbon dissolves into the molten metal. Under these conditions, graphite breaks down and the carbon atoms enter solution in the metal.
5. Carbon atoms migrate to the cooler diamond seed. A subtle temperature gradient drives the dissolved carbon toward the seed.
6. Diamond crystallizes onto the seed, layer by layer. Over the course of days to weeks, the seed grows into a larger rough diamond.
7. The chamber is depressurized and cooled. The diamond is removed, cleaned, and prepared for cutting.

HPHT growth time

A 1 carat HPHT diamond typically takes 3-7 days to grow. Larger stones (3+ carats) can take 2-3 weeks. The process is power-intensive throughout — the high pressure and temperature must be sustained for the entire duration.

HPHT diamond characteristics

• Often shows cubo-octahedral growth patterns visible only under specialized gemological equipment
• May contain trace metallic inclusions from the metal catalyst (rare in gem-quality stones, common in industrial-grade)
• Excellent for fancy yellow diamonds — HPHT can produce strong yellow color through controlled nitrogen exposure
• Typically faster to produce than CVD for stones under 2 carats

Method 2: CVD (Chemical Vapor Deposition)

CVD takes a fundamentally different approach. Rather than using extreme pressure, CVD grows diamonds atom by atom from carbon-rich gas at relatively low pressure (close to vacuum). The method was pioneered for industrial diamond coatings and refined for gem-quality production over the past decade.

The CVD process step by step

1. A flat diamond seed is placed inside a vacuum chamber. CVD seeds are typically thin square plates that determine the orientation of the growing crystal.
2. Carbon-rich gas is introduced. The gas is usually a mixture of methane (CH₄) and hydrogen, with methane providing the carbon source.
3. The gas is energized to extreme temperatures. Microwave energy or hot filaments break the gas down into a plasma at temperatures of 700-1,300°C.
4. The plasma decomposes the methane molecules. The carbon atoms separate from the hydrogen atoms.
5. Carbon atoms settle onto the diamond seed. They bond into the diamond crystal structure, layer by atomic layer.
6. The diamond grows upward, perpendicular to the seed plate. Growth happens at roughly 0.1-0.3 mm per hour — slow but steady and highly controllable.
7. Hydrogen atoms scrub away non-diamond carbon (graphite) that would otherwise contaminate the crystal.
8. The diamond is removed from the chamber, cleaned, and prepared for cutting.

CVD growth time

A 1 carat CVD diamond typically takes 4-6 weeks to grow. Larger stones can take 2-3 months. The process is much slower per stone than HPHT, but multiple diamonds can grow in the same chamber simultaneously.

CVD diamond characteristics

• Cuboid growth structure visible only under specialized gemological equipment
• Higher purity than HPHT — fewer trace impurities since no metal catalyst is involved
• Excellent for D-color colorless diamonds — the controlled growth conditions produce extremely pure stones
• Capable of growing very large stones with proper equipment
• Often the preferred method for fancy color lab grown diamonds requiring specific color tuning

HPHT vs CVD: side-by-side comparison

Attribute	HPHT	CVD
Pressure	5-6 GPa (extreme)	Near-vacuum (low)
Temperature	1,300-1,600°C	700-1,300°C
Carbon source	Solid graphite + metal catalyst	Methane gas
Growth time (1 ct)	3-7 days	4-6 weeks
Crystal growth pattern	Cubo-octahedral	Cuboid (perpendicular layers)
Best for colorless	Good (G-J color typical)	Excellent (D-F color achievable)
Best for fancy yellow	Excellent	Good
Trace impurities	Possible metallic traces	Minimal
Energy intensity	Higher per stone	Lower per stone
Maximum size achievable	Generally smaller	Larger stones possible

Are CVD diamonds better than HPHT diamonds (or vice versa)?

Honest answer: neither is universally better. Both methods produce real, beautiful diamonds. The right method depends on the specific stone you're producing:

• For top-tier colorless diamonds (D-F color): CVD typically produces the highest-quality stones. Most premium colorless lab grown diamonds at Mohana Jewels are CVD.
• For fancy yellow diamonds: HPHT is often preferred because it can produce intense yellow color through controlled nitrogen exposure during growth.
• For fancy pink, blue, and green: Both methods can produce these colors, often with post-growth treatments to develop specific saturation.
• For very large stones (5+ carats): CVD is typically the better choice because growth conditions can be sustained for longer periods.

Most reputable retailers (including Mohana Jewels) work with both methods, choosing whichever produces the best stone for each piece. The grade — measured by IGI or GIA on the same 4Cs framework regardless of growth method — is what actually matters when you're buying.

How to tell if a lab grown diamond is CVD or HPHT

You can't tell by eye. Even with 10x magnification, lab grown diamonds from both methods look identical to each other and to mined diamonds. The differences are detectable only with specialized gemological equipment:

• GIA iD100: Differentiates lab grown from mined; can sometimes identify CVD vs HPHT
• DiamondView: Shows fluorescence patterns that reveal crystal growth structure (cubo-octahedral for HPHT vs cuboid for CVD)
• Spectroscopy equipment: Detects trace impurities and structural defects unique to each growth method

For everyday wear and routine jewelry purchases, you don't need to know whether your diamond is CVD or HPHT. The certificate from GIA or IGI grades the stone on the same 4Cs framework regardless of method.

How long does it take to make a lab grown diamond?

Total time from "press start" to a finished, set engagement ring depends on the size, method, and post-growth processing required:

• Small stones (under 1 carat): 3-14 days of growth + 1-2 weeks of cutting and polishing + 1-3 weeks of setting = approximately 4-8 weeks total
• 1-2 carat stones: 4-6 weeks of growth + 2-3 weeks of cutting/polishing + 2-4 weeks of setting = approximately 8-13 weeks total
• 3+ carat stones: 6-12 weeks of growth + 3-6 weeks of cutting/polishing + 3-6 weeks of setting = approximately 12-24 weeks total

The growth itself is only one piece. The cutting, polishing, certification, and setting steps add weeks to months on top. This is why custom lab grown engagement rings typically take 4-6 weeks from approved CAD rendering to delivery — the setting and final preparation account for most of that time, with the loose stone often already in inventory.

What happens after the diamond grows?

Once a rough diamond is removed from the growth chamber, it goes through several more steps before reaching your finger:

1. Initial inspection. The rough is examined for shape, internal characteristics, and growth quality.
2. Planning. Computer modeling determines the most efficient cut to maximize finished carat weight while achieving the best 4Cs grades.
3. Sawing. The rough is sawed into smaller blocks if necessary to allow multiple finished stones from a single rough.
4. Bruting. The rough block is shaped to its general outline (round, oval, cushion, etc.).
5. Faceting. Each individual facet is ground onto the diamond. A round brilliant has 58 facets; complex cuts can have 70+.
6. Polishing. The faceted diamond is polished to a mirror finish on each facet.
7. Cleaning. The diamond is ultrasonically cleaned to remove all polishing residue.
8. Certification. The diamond is sent to a gemological laboratory (GIA or IGI) for grading and laser inscription of the certificate number.
9. Setting. The certified diamond is set into the final piece of jewelry by a master craftsman.
10. Final inspection and shipping. The completed piece undergoes quality inspection and is shipped insured to the customer.

The same craftsmen who cut and polish mined diamonds work on lab grown diamonds — using the same equipment, the same techniques, and the same standards. There's no functional difference in how the two are processed once they exist as rough crystals.

Is the lab grown diamond growth process eco-friendly?

Lab grown diamond production has a significantly smaller environmental footprint than mining — but it's not zero-impact. The honest accounting:

Where lab grown wins clearly

• Land use: Industrial facility footprint vs hundreds to thousands of acres for open-pit mining
• Water use: Far less per carat (mining requires hundreds of gallons; lab requires a fraction of that)
• Wildlife and ecosystems: No habitat disruption
• Community impact: No displaced communities

Where it's nuanced

• Energy intensity: Both HPHT and CVD require significant sustained energy. The carbon footprint per carat depends heavily on the energy source.
• Renewable energy makes the difference: Lab grown diamonds from facilities powered by solar, wind, or hydro have dramatically lower carbon footprints than those from grid-electricity facilities in fossil-fuel-heavy regions.

The leading lab grown diamond producers — including the labs Mohana Jewels sources from — increasingly use renewable energy specifically to address this concern. Read our full sustainability story for the specifics on how our diamonds are produced.

Should you care whether your diamond is CVD or HPHT?

For 95% of buyers, no. What matters is the diamond's actual quality (the 4Cs), the certification (GIA or IGI), and how it looks in person. A high-quality CVD diamond and a high-quality HPHT diamond of the same 4Cs grades are visually indistinguishable.

You might care about the production method if:

• You're specifically interested in the highest-purity colorless diamonds (CVD often delivers slightly better D-F grades)
• You're shopping for a fancy yellow diamond (HPHT typically produces stronger yellow color)
• You're personally curious about the technology behind your stone

Otherwise, focus on the 4Cs and certification. The growth method is an industrial detail that doesn't affect the final visual or performance of the diamond.

The bottom line

Lab grown diamonds are made through one of two methods — HPHT (recreating extreme earth-mantle conditions) or CVD (building diamonds atom by atom from carbon gas). Both methods produce real diamonds with identical chemistry, brilliance, and certification standards as mined diamonds. CVD typically excels at top-tier colorless production; HPHT often excels at fancy yellow production. Both methods are continually improving, and most reputable retailers (Mohana Jewels included) work with both depending on which produces the best stone for each piece.

For most buyers, the production method is an interesting backstory rather than a buying decision. Focus on the 4Cs, insist on IGI or GIA certification, and choose a stone that looks beautiful to you. Browse our complete lab grown diamond engagement ring collection, view our best sellers, or contact us for a free consultation to talk through your options.

Frequently asked questions

How are lab grown diamonds made?

Lab grown diamonds are made using one of two methods: HPHT (High Pressure High Temperature), which recreates earth-mantle conditions to crystallize carbon onto a diamond seed; or CVD (Chemical Vapor Deposition), which uses carbon-rich gas heated to extreme temperatures to deposit carbon atoms onto a seed layer by layer. Both methods produce real diamonds in 4-10 weeks.

Are CVD diamonds better than HPHT diamonds?

Neither is universally better. CVD typically produces the highest-quality colorless diamonds (D-F color). HPHT typically produces the strongest fancy yellow diamonds. For most buyers, the quality grades on the GIA or IGI certificate matter far more than the growth method.

How long does it take to grow a lab grown diamond?

A 1 carat lab grown diamond takes approximately 3-7 days via HPHT or 4-6 weeks via CVD. Larger stones take longer — 3+ carat diamonds can take 2-3 months to grow. Total time from rough crystal to finished jewelry, including cutting, polishing, certification, and setting, typically runs 8-13 weeks for a 1-2 carat engagement ring.

Can a jeweler tell if a lab grown diamond is CVD or HPHT?

Not by eye. Even with 10x magnification, CVD and HPHT diamonds look identical. Specialized gemological equipment (GIA iD100, DiamondView, spectroscopy) can identify the production method, but no everyday jewelry tool can.

Are lab grown diamond production methods eco-friendly?

Lab grown production has a significantly smaller environmental footprint than mining (no land disruption, less water, no displaced communities). However, both HPHT and CVD are energy-intensive — the carbon footprint per carat depends heavily on whether the production facility uses renewable energy. The leading producers, including those Mohana Jewels sources from, increasingly use renewable energy.