HPHT vs. CVD Lab-Grown Diamonds: Understanding the Science
When clients learn that lab-grown diamonds are structurally, chemically, and optically identical to earth-mined diamonds, the next question is usually: How are they made?
Every lab-grown diamond begins with a "seed"—a microscopic slice of a diamond (either natural or previously lab-grown). From there, scientists use one of two advanced technological processes to grow a new diamond layer by layer. Both methods yield 100% genuine diamonds with a Mohs hardness of 10, but they mimic the creation process in very different ways.
Here is what you need to know about the two methods: HPHT and CVD.
Every lab-grown diamond begins with a "seed"—a microscopic slice of a diamond (either natural or previously lab-grown). From there, scientists use one of two advanced technological processes to grow a new diamond layer by layer. Both methods yield 100% genuine diamonds with a Mohs hardness of 10, but they mimic the creation process in very different ways.
Here is what you need to know about the two methods: HPHT and CVD.
HPHT (High Pressure-High Temperature)
The HPHT method creates diamonds by replicating the extreme geological conditions found deep within the Earth’s mantle.
- The Environment: The diamond seed is placed into a specialized press alongside pure solid carbon.
- The Conditions: The chamber is subjected to crushing pressure and extreme heat—often exceeding 4,500 degrees Fahrenheit.
- The Result: Under these intense conditions, the carbon melts and begins to crystallize around the starter seed. As it cools, a genuine diamond is formed, replicating the exact way a natural diamond grows over millions of years, but accelerated into a matter of weeks.
CVD (Chemical Vapor Deposition)
Rather than mimicking the crushing pressure of the Earth, the CVD method grows diamonds in a high-tech laboratory vacuum.
- The Environment: The diamond seed is placed inside a sealed vacuum chamber which is filled with carbon-rich gases (like methane).
- The Conditions: The chamber is heated using microwave energy until the gas breaks down into a plasma vapor.
- The Result: The carbon atoms separate from the gas and rain down onto the diamond seed, crystallizing layer by microscopic layer to form a new diamond.
Post-Growth Treatments and Color Tints
In the early days of lab-grown technology, CVD diamonds occasionally grew with undesirable yellowish or brownish tints, and there were rumors of stones reacting poorly to UV light.
Today, advancements in manufacturing have largely eliminated these issues. However, because raw CVD diamonds can still occasionally exhibit a greyish or brown undertone, they are often put through an HPHT treatment after they are grown to stabilize and perfect their bright white color.
Today, advancements in manufacturing have largely eliminated these issues. However, because raw CVD diamonds can still occasionally exhibit a greyish or brown undertone, they are often put through an HPHT treatment after they are grown to stabilize and perfect their bright white color.
The JMD Master-Level Difference
Whether a diamond is grown via HPHT or CVD, the final result is a true diamond. However, not all lab-grown diamonds are created equal. Poorly grown stones from either method can feature strange growth striations, blurry crystal structures, or hidden blue and grey color tints that a traditional grading report might not clearly disclose.
At Joel McFadden Designs, we do not expect you to navigate the complexities of diamond growth alone. We use our decades of bench experience to meticulously evaluate and curate every lab-grown diamond we present, ensuring your gemstones feature flawless crystal integrity, brilliant light performance, and no undesirable undertones.
At Joel McFadden Designs, we do not expect you to navigate the complexities of diamond growth alone. We use our decades of bench experience to meticulously evaluate and curate every lab-grown diamond we present, ensuring your gemstones feature flawless crystal integrity, brilliant light performance, and no undesirable undertones.