What is HPHT Lab-Grown Diamonds? Everything You Need to Know

Lab-grown diamonds have been steadily gaining popularity in recent years due to their ethical sourcing, environmental sustainability, and affordability. Among the methods used to create these diamonds, HPHT (High Pressure High Temperature) is one of the most established and widely used techniques. In this guide, we’ll explore everything you need to know about HPHT lab-grown diamonds—from how they are made to how they compare with other synthetic diamonds.

What Is HPHT Lab-Grown Diamonds?

HPHT lab-grown diamonds are synthetic diamonds produced using the High Pressure High Temperature method. This process simulates the natural conditions under which diamonds form deep within the Earth. Just like mined diamonds, HPHT diamonds are made of pure carbon arranged in a crystal structure, making them physically, chemically, and optically identical to natural diamonds.

HPHT diamonds are not diamond simulants (like cubic zirconia or moissanite); they are real diamonds—just grown in a laboratory setting. The key distinction lies in their origin. Natural diamonds take billions of years to form underground, whereas HPHT diamonds can be produced in a few weeks.

How Are HPHT Lab Grown Diamonds Made?

The HPHT process involves recreating the high pressure and high temperature conditions found in the Earth’s mantle where natural diamonds form.

Here’s a step-by-step breakdown of how HPHT diamonds are created:

Diamond Seed Placement: The process starts with a small diamond seed—usually a sliver of another diamond—placed inside a carbon source.
Application of Pressure and Heat: The seed and carbon source are then placed inside a press. Three types of presses are commonly used: cubic press, belt press, and split-sphere (BARS) press. The temperature is raised to over 1,300°C (2,372°F) and pressure to about 5–6 GPa (gigapascals)—similar to the conditions 140-190 km beneath the Earth’s surface.
Diamond Growth: Under these extreme conditions, the carbon melts and starts to crystallize around the seed, gradually forming a diamond.
Cooling and Finishing: Once the diamond reaches the desired size, it is slowly cooled, removed from the press, and cut and polished like a natural diamond.

The entire growth process can take several days to weeks, depending on the size and quality of the diamond being produced.

Features of HPHT Lab-Grown Diamonds

HPHT diamonds have several distinguishing features that make them a popular choice for consumers and jewelers:

Identical to Natural Diamonds: Physically, chemically, and optically, HPHT diamonds are the same as mined diamonds.
Clarity and Color Enhancement: HPHT treatment is often used to improve the clarity or color of a diamond, especially in naturally mined diamonds.
Cost-Effective: HPHT lab-grown diamonds are usually 30–40% cheaper than natural diamonds of the same quality.
Environmentally Friendly: Lab-grown diamonds significantly reduce the environmental and ethical concerns associated with traditional mining.
High Purity: HPHT diamonds can be Type IIa, the most chemically pure type of diamond, which is extremely rare in nature.
Color Variety: HPHT diamonds can be grown in a range of colors, including white, blue, yellow, and pink.

CVD vs HPHT Diamonds: What’s the Difference?

Both HPHT (High Pressure High Temperature) and CVD (Chemical Vapor Deposition) are methods used to grow diamonds in a lab, but they differ significantly in technique and outcome.

Feature	HPHT Diamonds	CVD Diamonds
Process	Mimics Earth’s natural diamond-forming environment using high pressure and temperature	Uses a carbon-rich gas in a vacuum chamber to deposit layers of carbon
Growth Direction	Grows from center outward	Grows vertically layer by layer
Color	Naturally tends toward yellow or brown due to nitrogen	Typically whiter but may require post-treatment
Crystal Structure	Often includes metallic inclusions	Can show striations or graining
Cost	Slightly higher due to energy-intensive process	Generally more cost-effective for producing large quantities

Which is better?

It depends on what you’re looking for. HPHT diamonds tend to have better crystal integrity and are more likely to be Type IIa, which are extremely pure. CVD diamonds offer excellent color control and are often used for larger, colorless stones.

Why Choose a HPHT Lab-Grown Diamond?

If you’re in the market for a diamond that combines beauty, value, and ethical sourcing, HPHT lab-grown diamonds offer compelling advantages:

Affordability Without Compromise: You get a real diamond at a fraction of the cost of a mined one, without sacrificing quality or appearance.
Ethical Sourcing: HPHT diamonds are conflict-free, helping you avoid supporting potentially exploitative mining operations.
High Purity and Quality: The HPHT process can produce gem-quality diamonds with excellent clarity, especially in the Type IIa category.
Durability: With a Mohs hardness of 10, HPHT diamonds are just as durable and long-lasting as their natural counterparts.
Innovation and Technology: Choosing an HPHT diamond supports a sustainable, high-tech approach to luxury—ideal for the modern consumer.

FAQs About HPHT Lab-Grown Diamonds

Que: Are HPHT diamonds real diamonds?

Ans: Yes. HPHT diamonds are 100% real diamonds, both chemically and physically. They are not simulants like moissanite or cubic zirconia.

Que: Can HPHT diamonds be distinguished from natural diamonds?

Ans: To the naked eye, no. Even trained gemologists often require specialized equipment, such as spectroscopy or photoluminescence tools, to identify lab-grown diamonds. Gem certification labs like GIA or IGI can distinguish them using advanced techniques.

Que: Do HPHT diamonds lose their sparkle over time?

Ans: No. Like natural diamonds, HPHT diamonds maintain their brilliance, fire, and luster for life if properly cared for.

Que: Are HPHT diamonds more expensive than CVD diamonds?

Ans: Generally, yes. The HPHT process is more energy-intensive and may involve more expensive machinery, making these diamonds slightly more costly than CVD diamonds, though still cheaper than mined diamonds.

Que: Is it safe to buy an HPHT diamond?

Ans: Absolutely. As long as you buy from a reputable dealer and request a certificate from a recognized gemological lab, such as IGI or GIA, you can be confident in your purchase.

Que: Can HPHT diamonds be used for engagement rings?

Ans: Yes. They are perfect for engagement rings, offering the same beauty and durability as mined diamonds at a lower price and with greater ethical assurance.

Que: Are there any downsides to HPHT diamonds?

Ans: The main considerations are that some HPHT diamonds might show metallic inclusions or color tints, depending on the process. However, high-quality HPHT diamonds that meet gem standards are comparable in beauty and quality to natural diamonds.

Final Thoughts

HPHT lab-grown diamonds represent a fusion of science and elegance. Offering beauty, durability, ethical sourcing, and affordability, these diamonds are a smart choice for consumers looking for an alternative to mined stones. Whether you're buying an engagement ring or a statement piece, HPHT diamonds offer timeless sparkle—without compromise.