How Are Lab Grown Diamonds Made? CVD vs HPHT, Explained Simply

Lab grown diamonds are made by recreating the conditions that form a diamond underground, but doing it inside a machine over a few weeks instead of over a billion years. A tiny diamond seed is exposed to intense heat and pressure, or to carbon-rich gas, until new carbon atoms lock onto it in the same crystal pattern as a mined diamond. There are two methods that do this: HPHT (High Pressure High Temperature) and CVD (Chemical Vapor Deposition). Both produce a real diamond that is chemically and optically identical to one pulled from the ground.

That is the short answer. Below we break down each method in plain terms, explain why the result is genuinely a diamond and not a fake, how long the process takes, and why all of this lands at a lower price than mined stones.

The two ways lab grown diamonds are made

Every lab grown diamond starts with a diamond seed, which is a thin slice of an existing diamond. From there, the two methods take different paths to grow more diamond on top of that seed.

HPHT: High Pressure High Temperature

HPHT copies what happens deep in the earth. The diamond seed is placed in a chamber with pure carbon (usually graphite) and a metal catalyst. The machine then applies pressure of roughly 5-6 gigapascals (about 50,000-60,000 times normal air pressure) and temperatures near 1,300-1,600 degrees Celsius.

Under those conditions the carbon melts, then crystallizes onto the seed, building up a larger diamond layer by layer. HPHT is the older of the two methods and tends to grow stones efficiently. It is also the technique used to improve the color of some diamonds after growth.

CVD: Chemical Vapor Deposition

CVD takes a gentler, more recent approach. The diamond seed sits in a sealed vacuum chamber that gets filled with carbon-rich gas, typically methane and hydrogen. The chamber is heated and the gas is energized into a plasma, which breaks the molecules apart. Free carbon atoms then rain down onto the seed and bond to it, growing the diamond upward in flat layers.

CVD runs at lower pressure than HPHT, which gives growers fine control over the conditions. This control is one reason CVD has become popular for producing larger, high-clarity stones. Some CVD diamonds also get a quick HPHT treatment afterward to fine-tune their color, so the two methods are not always either-or.

Why a lab grown diamond is a real diamond

This is the part people get stuck on, so it is worth being direct. A diamond is just carbon arranged in a specific cubic crystal structure. A lab grown diamond has the exact same carbon, the same structure, the same hardness (10 on the Mohs scale), the same sparkle, and the same way of bending light. It is not a simulant.

That last word matters. Cubic zirconia and moissanite are simulants, meaning they look like diamonds but are made of different materials and test as non-diamond. A lab grown diamond is not in that category. Put one next to a mined diamond of the same specs and even a trained jeweler cannot tell them apart by eye. The only reliable way to separate the two is specialized equipment that reads tiny growth markers, which is exactly what gemological labs use.

Speaking of which, lab grown diamonds are graded by the same independent labs that grade mined ones. Reputable lab grown stones come with an IGI or GIA certificate covering the same 4Cs (cut, color, clarity, and carat) and noting that the diamond is laboratory grown. So you are not taking anyone's word for it. You are buying a graded, certified diamond. You can sort and compare every certified stone in our diamond search tool the same way you would shop mined inventory.

How long does it take to grow a diamond?

Most lab grown diamonds take roughly 2-4 weeks to grow, depending on the size and method. A larger or higher-clarity stone takes longer because growers slow the process down to keep the crystal clean. Compare that to the natural version, which forms over 1-3 billion years under the earth before being mined, transported, and cut. Same end product, very different timeline.

After growth, the rough diamond is cut and polished by hand exactly like a mined rough. That cutting stage takes the same skill and time either way, because the physical material reacts to the wheel identically.

Why lab grown diamonds cost less

Lower price is the most common reason people choose lab grown, and it is not because the diamond is lesser. It comes down to the supply chain.

• No mining. There is no excavation, no heavy equipment, no large tracts of land, and none of the cost of pulling tons of earth to find a few carats.
• Shorter chain. A mined diamond passes through many hands between the ground and the store. A lab grown diamond skips most of those middle steps.
• Predictable supply. Growers can produce to demand instead of relying on what a mine happens to yield, which keeps pricing steadier.

The result is that a lab grown diamond typically costs about 40-70% less than a mined diamond of comparable cut, color, clarity, and carat. In practice that means a noticeably larger or cleaner stone for the same budget. You can read more on the full comparison on our lab grown diamonds page.

One honest caveat, since we would rather you hear it from us. Lab grown diamonds generally have lower resale value than mined diamonds, partly because growing technology keeps improving and supply keeps expanding. If you are buying a ring to wear and keep, this rarely matters. If you think of jewelry mainly as a financial asset, it is worth knowing going in.

Frequently asked questions

Are lab grown diamonds fake?

No. They are real diamonds with the same chemical makeup, crystal structure, and physical properties as mined diamonds. They are graded and certified by labs like IGI and GIA. Only simulants such as cubic zirconia and moissanite are non-diamonds, and lab grown stones are not simulants.

Can a jeweler tell a lab grown diamond from a mined one?

Not by eye. The two are visually identical at the same specs. Separating them requires specialized lab equipment that reads microscopic growth patterns. Every certified lab grown diamond is also laser-inscribed and noted as lab grown on its certificate.

Is CVD or HPHT better?

Neither is universally better. Both produce real, gem-quality diamonds, and a finished stone's quality comes down to its cut, color, clarity, and carat rather than the growth method. Once cut and certified, you are choosing a diamond on its 4Cs, not on whether it was grown by CVD or HPHT.

Build your ring around a certified lab grown diamond

Now that you know how the diamond itself is made, the fun part is picking one. Browse certified lab grown stones by cut, color, clarity, carat, and budget in our diamond search, then set it in the design you want. Every Diyona ring is made to order, ships with documentation, and is backed by a lifetime warranty on manufacturing defects, with a 30-day return window if it is not right. We are online only, so you get direct pricing without the markup of a storefront.