Consumers looking for alternatives to mined diamonds will discover a wealth of options to choose from, from simulants like cubic zirconia and moissanite to lab-grown diamonds. While cubic zirconia and moissanite are stones that look like diamonds but have different chemical compositions, lab-grown diamonds are chemically identical to mined diamonds, making them the superior choice. The difference is that it takes nature millions of years to make a diamond, but we can grow one in a matter of weeks.
All lab-grown diamonds are grown using either the High Pressure, High Temperature (HPHT) method or the Chemical Vapor Deposition (CVD) method. Both methods start with a diamond seed, taken either from a mined or a lab-grown specimen. And both methods are capable of producing clear, colorless diamonds of the highest quality.
As knowledge of the natural world advanced through the 18th and 19th centuries, scientists began to draw a clearer picture of the way minerals form underground. Some gemstones, for example, are formed when mineral-rich water deposits minerals into cavities in the Earth’s surface. Those minerals are layered and compressed over millions of years, forming gemstones like opal. Others are formed when intense heat and pressure melts rock, which then cools and hardens into a new shape: a crystal matrix. Diamonds are formed when this heat and pressure rearranges pure carbon from its typical flat 2D shape to a 3D crystal.
Once scientists understood more about this process, they began trying to replicate it in a laboratory setting. (Read more about this fascinating history here [link: https://primolabgrown.com/blog-menu/12-lab-grown-diamonds-a-century-of-growth]). The results of these experiments are the two main methods for growing diamonds used today: HPHT and CVD.
High Pressure, High Temperature (HPHT)
The High Pressure, High Temperature method was the first to produce gemstone-quality diamonds. This process mimics the way diamonds form in nature. A diamond seed, surrounded by carbon, is placed in a press and subjected to extreme heat and pressure—1300-1600°C and 870,000 psi, the same heat and pressure at which diamonds form in the upper mantle. The carbon melts in a molten solution of nickel and iron, and as it cools, the carbon atoms crystalize around the diamond seed, adding layers of pure carbon to the diamond, effectively growing a diamond around the original seed.
Just like mined diamonds, HPHT diamonds often contain minute traces of nitrogen or boron. Nitrogen can give a diamond a yellow tint, while boron can be added to create blue diamonds. But that isn’t to say that diamonds grown using the HPHT method are only yellow or blue. The HPHT method can produce the full range of diamond colors, including colorless diamonds.
Chemical Vapor Deposition (CVD)
The CVD method is a more recent development that follows roughly the same principle of growing a diamond by adding layers of carbon to an existing diamond seed. The difference is that the CVD method requires much lower temperatures and pressures by using microwaves and vapor. It works like this: the diamond seed is placed into a vacuum chamber, and the chamber is then filled with hydrocarbon gas. The gas is heated and bombarded with a microwave beam, which separates the hydrogen from the carbon. The carbon then bonds with the diamond seed, growing a diamond one carbon atom at a time.
It is often said that CVD method produces type IIA diamonds, which are colorless, extremely pure, and extremely rare in nature, containing almost no nitrogen or boron. This isn’t exactly true; while CVD diamonds are chemically pure, the diamond that comes out of the chamber is often brown in color. These brown diamonds are then decolorized by post-growth HPHT treatment.
It was once quite difficult to produce a colorless diamond using the HPHT method, but technological advancements and the refinement of techniques has made it much easier. We only sell the highest quality diamonds we produce, and all of our diamonds are sold as-grown, with no post-growth HPHT color treatment.
