When buyers research lab grown diamonds, they inevitably encounter the terms CVD and HPHT — the two main processes for growing diamonds in a laboratory. The question that follows is always some version of: "Which one is better?" The answer requires understanding both processes, but it ends in the same place: for most buyers, the distinction matters far less than the quality grades on the IGI certificate.
How CVD Diamonds Are Made (The 30-Second Version)
CVD stands for Chemical Vapour Deposition. The process works as follows: a thin slice of diamond (the "seed crystal") is placed inside a vacuum chamber. A mixture of carbon-rich gases — typically methane and hydrogen — is introduced into the chamber. The gases are activated by microwave energy or a hot filament, causing the carbon atoms to separate from the gas molecules and deposit onto the diamond seed crystal, building the diamond up layer by layer.
CVD growth happens at relatively low pressures (compared to Earth's mantle or HPHT conditions) but at temperatures of 700-1,300°C. The process can be controlled very precisely, which allows producers to influence the crystal's growth direction and minimise certain types of inclusions. CVD diamonds typically grow as a roughly cuboid crystal form that is then cut and polished into the final diamond shape.
The CVD process is the dominant production method for gem-quality lab grown diamonds sold in India today.
How HPHT Diamonds Are Made (The 30-Second Version)
HPHT stands for High Pressure High Temperature. This process more directly mimics the conditions under which natural diamonds form in the Earth's mantle. A diamond seed crystal is placed with a carbon source (graphite or diamond powder) inside a press that applies both high pressure (typically 5-6 GPa — equivalent to 50,000-60,000 atmospheres) and high temperature (1,300-1,600°C).
Under these conditions, the carbon source dissolves in a metallic catalyst and then recrystallises onto the diamond seed, growing the crystal outward from the seed. The growth pattern in HPHT tends to be octahedral (following the natural crystal growth directions of diamond), which is why HPHT diamonds often have a slightly different internal growth pattern than CVD diamonds when viewed under spectroscopic analysis.
HPHT was the first industrial method for growing gem-quality diamonds and is still widely used. It is also used to enhance the colour of some diamonds — a process called HPHT treatment, which is disclosed on the IGI certificate.
Chemical and Physical Differences: What Science Confirms
Both CVD and HPHT diamonds are chemically pure carbon in the diamond crystal structure. They have the same Mohs hardness (10), the same refractive index (2.417), the same thermal conductivity, and the same density. These are the properties that define diamond as a material, and they are identical in both types.
There are trace differences that advanced spectroscopic analysis can detect: nitrogen distribution patterns differ between CVD and HPHT growth, and boron is sometimes present in CVD diamonds that exhibit blue coloration from boron doping. These trace differences are not visible to the eye and do not affect the diamond's appearance, durability, or performance. They are growth signatures — evidence of how the crystal formed — rather than quality differences.
Quality Differences: Does One Process Produce Better Diamonds?
The honest answer: no. Both processes produce diamonds across the full quality spectrum from high-colour, high-clarity, Excellent-cut stones to lower-specification diamonds. The quality of a specific diamond depends on the growth conditions, the expertise of the production facility, and the cutting and polishing standards applied — not on whether it was grown by CVD or HPHT.
High-quality CVD diamonds (D-F colour, VVS clarity, Excellent cut) are exceptional gemstones. High-quality HPHT diamonds at the same specifications are equally exceptional. A G VS2 CVD diamond and a G VS2 HPHT diamond, both graded by IGI, represent the same quality level. The certificate grade is what defines quality — not the growth process.
One practical note: CVD diamonds occasionally exhibit a slight greyish or brownish undertone during growth that is removed through post-growth HPHT treatment. This treatment is disclosed on the IGI certificate. It does not affect the diamond's quality or durability — it is a finishing process that brings the colour grade to its final level.
Price Differences Between CVD and HPHT
In the Indian market, well-cut CVD and HPHT diamonds at the same IGI-certified quality specification are priced comparably. There is no consistent premium for one process over the other at the retail level. Prices are driven by the 4Cs documented in the IGI certificate, not by the growth method.
Some buyers ask specifically for HPHT because of the "closer to natural conditions" narrative. This is not a quality argument — it is a philosophical preference that does not correspond to any measurable difference in the finished diamond.
What IGI Certification Says About Process vs Quality
The IGI grading report for a lab grown diamond discloses the growth method (CVD or HPHT) in the comments section. It does not grade the growth method — because the growth method is not a quality factor. The report grades cut, colour, clarity, and carat weight by the same standards applied to natural diamonds, because those are the dimensions that determine a diamond's quality and value.
When you see an IGI certificate that says "Laboratory Grown, CVD" or "Laboratory Grown, HPHT," the relevant quality information is in the 4C grades, not in the process disclosure. Read our full IGI certification guide.
What Nivara Uses and Why
Nivara sources primarily CVD lab grown diamonds because CVD production currently dominates the high-quality end of the Indian market and our sourcing relationships in the CVD segment allow us to access consistent quality at the grades our customers require. We source to IGI-certified specification — the process is a secondary consideration to the quality documentation.
If a specific HPHT stone meets a customer's brief and IGI specification, we will source it. The quality of the stone as documented by IGI is what matters. Our position is simple: buy the diamond, not the process. Browse our solitaires collection.
