The introduction of lab-grown diamonds to the diamond market may leave some consumers confused as to what they are actually getting when they purchase a lab-grown diamond. This is especially true as lab-grown diamonds become more and more affordable. In addition to being marketed under different names such as “synthetic” or “cultured” diamond, lab-grown diamonds may be confused with diamond simulants such as cubic zirconia. But the two are not the same. The difference is that lab-grown diamonds are chemically identical to mined diamonds, while cubic zirconia is a different substance entirely. Let’s get into exactly what that means.
A diamond, as you probably know already, is a mineral composed of about 99.95% carbon. Graphite and, to a lesser extent, coal are also mostly composed of carbon, but the difference is that in a diamond, intense heat and pressure have crystallized the carbon atoms into a three-dimensional lattice structure. Various other elements may comprise the other 0.05% of a diamond, and it's those trace elements that determine the color of a diamond: when nitrogen replaces carbon in parts of the crystal, you get a yellow diamond and the presence of boron leads to a blue diamond.
The process by which a flat chain of carbon atoms is restructured into a cubic crystal requires a great deal of heat and pressure. The heat and pressure required—1300°C (2400°F) and pressure 240,000 times the pressure found at sea level—occurs in the upper mantle, 150 km (90 miles) deep.
What are Lab-Grown Diamonds?
Throughout the 18th, 19th, and 20th centuries, scientists gained a more thorough understanding of the chemical composition of minerals and the geological processes that created them. In the 19th century, scientists like Henri Moissan hypothesized that the sort of heat and pressure required could be reproduced in a laboratory. Using the new electric technology of the day, he claimed to have grown diamonds.
Early attempts at growing diamonds resulted in stones too small and too brown to be of any value—if what was being created were diamonds at all and not a substance like silicon carbide. It wasn’t until the invention of the belt press that the dream of growing diamonds that were both useful to industry and gemstone-quality became a reality.
The belt press, invented by General Electric engineer Tracy Hall in 1954, produced temperatures of over 1600°C and 1.5 million pounds per square inch of pressure. This temperature was much lower than the 3500°C of Moissan’s electric arc furnace, but the pressure was far more than anyone in the late 1800s could have imagined possible.
The technique GE used to grow diamonds, called High Pressure, High Temperature (HPHT), did not produce diamonds large and clear enough to be used as gemstones until the 1970s. Around the same time, the Chemical Vapor Deposition (CVD) method began producing gemstone-quality diamonds. CVD grows diamonds at lower temperatures and pressures than HPHT by sealing a diamond seed in a chamber full of hydrocarbon gas. The chamber is then heated by microwaves, which breaks the hydrocarbon gas down into hydrogen and carbon. The carbon then bonds with the diamond seed, building a diamond crystal atom by atom.
Why “Lab-Grown”?
The result of both the HPHT and CVD methods is a crystalline mineral of almost pure carbon. A mineral composed of 99.95% or more carbon is a diamond, whether it was grown in molten rock under extreme heat and pressure in the upper mantle, in a gas-filled chamber heated by microwaves, or in the pressure of a mechanical press. For this reason, diamonds produced this way are referred to as “lab-grown” rather than synthetic. The term “synthetic” denotes a material produced by synthesis (combining two or more different substances) in order to imitate another substance. Lab-grown diamonds don’t imitate diamonds; they are diamonds. And since the methods produce actual diamonds, they are not “imitation” diamonds or “diamond simulants.” “Lab-grown diamond” is the most accurate way to describe the product of these processes.
What is Cubic Zirconia?
While lab-grown diamonds are chemically identical to diamonds, cubic zirconia (CZ) is a different substance altogether. Its brightness and clarity, not to mention its affordability, make it a great diamond simulant. But it is susceptible to dulling over time due to the accumulation of dirt. Nevertheless, it is almost indistinguishable from diamond to the untrained eye. But overall it is a far less durable stone. While diamond (both the mined and lab-grown kinds) rates a 10 on the Mohs hardness scale, the hardness of CZ is only 8. Nothing will scratch or chip a diamond, but CZ is likely to scratch, chip, and turn cloudy over years of daily use. This is because CZ is not a diamond but zirconium dioxide (ZrO2). It occurs rarely in nature; the cubic zirconia used in jewelry is synthesized by combining zirconium oxide powder with magnesium or calcium at 2750°C (4,982°F).
Whether your reasons for seeking an alternative to mined diamonds are about affordability or ethics, both cubic zirconia and lab-grown diamonds are both great alternatives. But only lab-grown diamonds are actual diamonds, with the same hardness, clarity, color, and unmistakable sparkle you expect from a diamond.
