CVD
Chemical vapour deposition — the dominant method for growing gem-quality lab diamonds. Carbon atoms from a gas plasma deposit onto a seed crystal, layer by layer, over 2–4 weeks.
CVD stands for chemical vapour deposition. In a CVD reactor, a thin diamond seed is placed in a low-pressure chamber filled with a hydrogen and methane gas mixture. Microwave energy ionises the gas into a plasma — a superheated cloud that breaks methane into reactive carbon species. These carbon atoms rain down onto the seed and bond in the same crystal structure as natural diamond.
The process produces Type IIa diamonds — the purest type, free of nitrogen impurities. Most natural diamonds are Type Ia (nitrogen-bearing); Type IIa naturals are exceptionally rare and valuable. CVD routinely produces Type IIa as its default, which is one reason CVD diamonds often have excellent clarity.
CVD has overtaken HPHT as the dominant lab-grown method because it is more scalable, produces thinner, larger plates of rough, and allows greater control over crystal quality. Since around 2018, CVD capacity has expanded dramatically, and lab-grown prices have fallen over 80%.
- FULL NAME
- Chemical vapour deposition
- GROWTH TIME
- 2–4 weeks / ct
- TYPE
- IIa (nitrogen-free)
Seed placement
A thin slice of diamond — the seed — is placed on a substrate plate inside the reactor chamber. The seed is typically a high-quality type IIa natural or HPHT diamond, polished to a precise surface. It provides the crystal template for growth.
Step 1 of 5 in the CVD process.
Gas introduction
The chamber is evacuated and then filled with a mixture of hydrocarbon gas (typically methane, CH₄) and hydrogen. The ratio is carefully controlled — usually 1–5% methane in hydrogen. This mixture is the carbon source from which the diamond will grow.
Step 2 of 5 in the CVD process.
Plasma activation
Microwave energy (or in some systems, a hot filament) ionises the gas into a plasma — a superheated cloud of ions and radicals. The plasma reaches temperatures of 3,000–5,000 K, breaking methane into reactive carbon species that can bond to the growing diamond surface.
Step 3 of 5 in the CVD process.
Layer-by-layer growth
Carbon atoms from the plasma deposit onto the seed crystal, bonding in the same tetrahedral structure as natural diamond. The stone grows upward at roughly 0.1–10 micrometres per hour — fast enough to grow a 1 ct rough in 2–4 weeks. Hydrogen etches away unwanted graphite, keeping the crystal pure.
Step 4 of 5 in the CVD process.
Cutting & grading
The resulting rough CVD diamond is cut and polished exactly like a natural diamond. It is then submitted for grading to GIA, IGI or other labs. The report notes "laboratory-grown" and may specify CVD or HPHT as the growth method. Optically and chemically it is identical to natural diamond.
Step 5 of 5 in the CVD process.
CVD vs HPHT
Two methods, one result — a genuine diamond. The difference is in how they get there.
Chemical vapour deposition
- Low pressure (~10–100 Torr), moderate temperature (~900°C)
- Grows from a gas plasma — no mechanical press needed
- Produces flat, plate-like rough crystals
- Naturally Type IIa — nitrogen-free, exceptionally pure
- Dominant method today; most scalable
- Sometimes shows brown tinting; can be corrected by HPHT post-treatment
High pressure, high temperature
- Very high pressure (~5–6 GPa), high temperature (~1,400°C)
- Mimics natural diamond formation conditions in the mantle
- Produces a cuboctahedral rough crystal — more 3D form
- Often Type Ib (contains nitrogen); can produce coloured diamonds
- Also used to treat natural diamonds (improve colour)
- More energy-intensive per carat; harder to scale
CVD vs natural diamond
Chemically identical. Optically identical. Commercially very different.
The CVD market
Lab-grown diamond production — dominated by CVD — has expanded at extraordinary speed since 2018. What was a niche product for industrial and scientific use has become a mainstream consumer option, with CVD diamonds now available at every major retailer.
Prices have fallen faster than almost any other consumer product. A 1 ct G VS1 CVD diamond that cost $4,000–5,000 in 2020 now sells for under $800 in 2026. The trajectory continues downward as more reactor capacity comes online globally, particularly in India and China.
This creates a clear value proposition for buyers who prioritise beauty per dollar and are not concerned with resale value. For buyers who view diamonds as a store of value or heirloom, natural diamonds retain advantages that CVD cannot replicate.
Price trajectory
−80%
Lab-grown prices since 2020
Driven by rapid expansion of CVD reactor capacity, primarily in India and China.
Market share
~20%
Lab-grown share of US engagement ring market (2025)
Up from under 2% in 2018. Growth has slowed as prices stabilise at lower levels.
Detection
100%
Detectable by GIA/IGI instruments
Modern spectroscopy reliably identifies all CVD and HPHT diamonds from natural.
Questions about CVD diamonds
Is a CVD diamond a "real" diamond?
Yes. A CVD diamond is chemically, physically and optically identical to a natural diamond — pure carbon in a tetrahedral crystal lattice. The Federal Trade Commission (FTC) ruled in 2018 that "laboratory-grown", "lab-created" and "synthetic" are all acceptable descriptors, but the stone itself is a diamond. GIA and IGI grade CVD diamonds on exactly the same 4Cs scale as natural diamonds.
What is the difference between CVD and HPHT?
CVD (chemical vapour deposition) grows diamond from a carbon-rich gas plasma at low pressure and moderate temperature (~800–1000°C). HPHT (high pressure, high temperature) replicates the conditions deep in the earth — around 5–6 GPa and 1,300–1,600°C — using a press to force carbon into diamond crystal structure. CVD is currently the dominant method for gem-quality lab-grown diamonds because it is easier to scale, produces larger crystals, and allows precise control over growth conditions. HPHT is also used to treat natural diamonds — improving colour after the fact.
Can I tell a CVD diamond from a natural just by looking?
No, not with the naked eye. CVD and natural diamonds are visually identical. Specialist equipment — photoluminescence spectroscopy, UV fluorescence, strain patterns under polarised light — can detect the growth method. GIA and IGI use these instruments during grading and note "laboratory-grown" on the report. Reputable sellers always disclose origin. Laser inscription on the girdle also typically identifies lab-grown stones.
Why are CVD diamonds cheaper than natural?
Supply. Natural diamonds take billions of years to form; the supply is finite and controlled by a small number of mining companies. CVD diamonds can be grown in weeks in a reactor and the technology is improving rapidly. Production capacity has expanded dramatically since 2018, driving prices down over 80% for lab-grown diamonds in that period. There is no equivalent scarcity premium for lab-grown stones. Compare natural vs lab-grown pricing in the DiamondTheGuide.
Do CVD diamonds hold their value?
Generally no. As production costs continue to fall and more CVD capacity comes online, resale prices for lab-grown diamonds have fallen sharply. A CVD diamond purchased in 2021 may be worth 60–80% less on the secondary market today. This contrasts with natural diamonds, which have historically held value better due to supply constraints. Buyers who prioritise value retention should consider natural; buyers who prioritise beauty-per-dollar should consider CVD.
Are CVD diamonds disclosed on grading reports?
Yes, always by reputable labs. GIA reports for laboratory-grown diamonds are printed on a distinct report format and clearly state "Laboratory-Grown Diamond". IGI reports are similar. The growth method (CVD or HPHT) is also typically noted. Both labs use advanced detection equipment. An undisclosed lab-grown diamond in a natural parcel is rare and constitutes fraud — the industry has significantly improved detection capabilities since 2015.