What Is an HPHT Diamond? High-Pressure High-Temperature Diamonds Explained

Short answer

HPHT stands for High Pressure, High Temperature — a method of growing real diamond in a lab by recreating the extreme conditions found roughly 150km underground, where natural diamonds form. HPHT diamonds are chemically and structurally identical to mined diamonds. HPHT is also used as a treatment on some natural diamonds to improve their color, so the term shows up in two related but different contexts — we’ll cover both below.

How HPHT growth actually works

A tiny diamond seed and a carbon source (often high-purity graphite) are placed together with a metal flux — typically iron, nickel, or cobalt, which acts as a solvent-catalyst.
The setup is loaded into a press capable of generating roughly 5–6 gigapascals of pressure — comparable to the weight of a commercial jet balanced on a fingertip — and heated to 1,300–1,600°C.
The metal flux melts the carbon source. Under that heat and pressure, carbon atoms dissolve into the molten metal.
Carbon crystallizes onto the seed. As conditions stabilize, dissolved carbon atoms migrate to the cooler seed crystal and bond onto it in diamond’s cubic lattice structure, growing the stone outward in all directions over several days to a couple of weeks.
The rough diamond is removed, cut, and polished, then graded exactly like any other diamond.

Because growth happens under pressure from multiple directions rather than flat, layer by layer, HPHT rough tends to form in the same cuboctahedral shapes natural diamond rough does — one reason HPHT stones can be harder to distinguish from natural diamonds without lab equipment than CVD stones are.

HPHT as a growth method vs HPHT as a treatment

This is where people get confused, so it’s worth separating clearly:

HPHT-grown diamond: the entire stone is created in the press, from seed to rough crystal. This is what this article is mainly about, and it’s always disclosed on the certificate as “laboratory-grown.”
HPHT-treated diamond: a natural rough diamond is put through the same high-pressure, high-temperature process afterward, not to grow it, but to alter trace impurities and improve its color (commonly turning brownish natural diamonds colorless, or creating fancy colors). This is a natural diamond that has been treated — a different thing from a lab-grown stone, and it must also be disclosed on the certificate.

Any diamond that’s been through either process should say so clearly on its GIA or IGI report. If a seller can’t show you a certificate, that’s the question to ask before you ask about price.

HPHT vs CVD: same result, different route

Both HPHT and CVD produce genuine diamond — pure carbon in a diamond crystal lattice, 10 on the Mohs scale, with identical brilliance and fire to a mined stone. The difference is entirely in the growing environment:

	HPHT	CVD
Method	Extreme pressure + heat (mimics the earth)	Carbon-rich gas + plasma, low pressure
Growth shape	Cuboctahedral (grows outward on multiple faces)	Tabular (grows flat, layer by layer)
Typical growth time	Days to ~2 weeks	2–4 weeks
Common in	Both loose stones and melee (small accent stones)	Larger, higher-clarity single stones

Neither method is “better” in a way that affects durability or beauty — a well-cut, well-graded stone is a well-cut, well-graded stone either way. For a full side-by-side against mined diamonds, see Natural vs CVD/HPHT diamonds.

Buying HPHT diamonds in Cambodia

At LAAR EK Jewelry (ហាងពេជ្រល្អឯក) in Phnom Penh, every HPHT diamond — loose or set into a finished piece — comes with an independent GIA or IGI certificate stating carat, cut, color, clarity, and growth method. We sell natural diamonds and CVD/HPHT lab-grown diamonds, wholesale and retail (មានលក់បោះដុំ និងរាយ ពេជ្រសុទ្ធ និង ពេជ្រ CVD/HPHT), so whichever you’re after, you’re covered.

Questions about a specific stone, or need a wholesale quote? Message us on Telegram — we’re open every day, 7:00 AM – 8:30 PM.