CVD vs HPHT Lab Grown Diamonds: How Each Is Made and How Gemologists Tell Them Apart

Lab grown diamonds are made in two main ways: HPHT, which recreates the crushing pressure and heat of the deep Earth inside a press, and CVD, which builds a diamond atom layer by atom layer from a carbon rich gas. Both produce real diamond with the same crystal structure as a mined stone, and gemologists can still tell the two methods apart. If you are comparing stones in Miami this season, knowing how each one was born helps you read a grading report with confidence.

What is a lab grown diamond, chemically?

A diamond is pure carbon arranged in a cubic crystal lattice, each atom bonded to four neighbors. That structure is why diamond is the hardest natural material and why it bends light so strongly. A lab grown diamond has the same lattice and the same chemistry. What differs is the story recorded inside it: growth patterns, trace elements and tiny inclusions that reveal how and where it formed.

We covered the bigger buying question in Natural vs Lab Grown Diamonds in 2026. Here we go one level deeper, into the machines.

How does HPHT diamond growth work?

HPHT stands for high pressure, high temperature. According to GIA's research on identifying lab grown diamonds, the growth chamber is heated to 1300 to 1600 °C at pressures above 870,000 pounds per square inch. GIA's Summer 2024 update in Gems & Gemology describes this as 5 to 6 GPa, equivalent to a depth of about 150 to 190 km inside the Earth.

The recipe, in simple terms:

• A small diamond seed sits inside a press.
• A carbon source, usually graphite, dissolves in a molten metal flux such as iron, nickel or cobalt.
• Carbon travels through the molten metal and crystallizes on the seed, over a period of hours to a few weeks.

Because of the way they grow, HPHT crystals typically show cube faces as well as octahedral faces. They can also trap tiny metallic inclusions from the flux, which is one of the clues gemologists look for.

How does CVD diamond growth work?

CVD stands for chemical vapor deposition. Instead of squeezing carbon, CVD builds diamond from a gas. GIA describes a vacuum chamber heated to about 900 to 1200 °C, where microwaves turn a gas mixture into a glowing plasma. The Gems & Gemology update notes that hydrogen makes up 90 to 99 percent of the mixture, with methane as the usual carbon source.

• Carbon atoms separate from the gas and settle on a flat diamond seed plate.
• The diamond grows upward in layers, forming flat, tabular crystals.
• According to GIA, growers remove the crystals every few days to polish the growth surface, and the full process can take three to four weeks.

CVD uses lower pressure than HPHT and less expensive equipment, but many CVD crystals come out brownish. GIA reports that about 80 percent of the CVD diamonds submitted to its labs since 2020 had post growth processing, typically an HPHT treatment at temperatures above 1600 °C, to improve color.

Which method is more common today?

GIA's Summer 2024 update says CVD diamonds now dominate the lab grown stones submitted for grading reports, having outnumbered HPHT submissions since around 2016. HPHT remains the main method for melee, the very small stones used in pavé, and most of those come from manufacturers in China.

How do gemologists tell HPHT from CVD?

Each method leaves fingerprints. Under the ultraviolet imaging GIA uses, natural diamonds show concentric growth patterns, HPHT diamonds show cross shaped patterns, and CVD diamonds show fine striations. Under polarized light, CVD stones often show banded strain while HPHT stones show little or none. Our article on how gemologists tell natural from lab grown diamonds walks through these tests in more detail.

GIA also notes something worth remembering: there is still no cheap, instant screening tool that definitively identifies every lab grown diamond. That is why a grading report from an independent lab matters.

Why Margaret works with natural diamonds

Margaret Krinetz Fine Jewelry, handmade in Tel Aviv and shipped to Miami, sets natural diamonds in its pieces. With a background in physics and biology, Margaret finds the lab grown story fascinating as science. She chooses natural stones because a diamond that formed deep in the Earth over geological time carries a story no machine can repeat.

The Sahara Ring holds an approximately 2 ct ethically sourced natural diamond, GIA certified, in 18K recycled gold.

Its sister piece, the Sahara Oval Diamond Ring, pairs an approximately 1 ct GIA certified natural oval diamond with a raw desert texture.

For earrings, the Diamond Studs in yellow gold carry 1.5 ct total of GIA certified natural diamonds, 0.75 ct each.

Frequently asked questions

Is a CVD diamond better than an HPHT diamond?

Neither is better by default. Both are real diamond. Judge each stone on its grading report: color, clarity, cut and any disclosed post growth treatment.

Can you see the difference between HPHT and CVD with the eye?

No. Separating them takes laboratory tools such as ultraviolet imaging, spectroscopy and strain analysis.

How long does delivery to Miami take?

Each piece is handmade to order in 4 to 6 weeks, then ships by DHL Express in 3 to 5 business days to Miami. Shipping is free on orders over $1,500.

Curious about natural diamonds with a story? Explore the engagement ring collection or write to the studio with your questions.