Education - Lab-Grown Diamonds

What are laboratory-grown diamonds?

Laboratory-grown diamonds have essentially the same chemical, optical and physical properties and crystal structure as natural diamonds. Like natural diamonds, they are made of tightly-bonded carbon atoms. They respond to light in the same way and are just as hard as natural diamonds. The main differences between laboratory-grown and natural diamonds lie in their origin. Think of it this way: laboratory-grown diamonds are like ice from your refrigerator, while natural diamonds are like ice from a glacier. They are both ice, although their formation stories and the age of each are very different.

Diamond Cut

Achieving the best cut for a diamond reflects in the stone’s final beauty and value. And of all the diamond 4Cs, it is the most complex and technically difficult to analyze. To determine the cut grade of the standard round brilliant diamond – the shape that dominates the majority of diamond jewelry – GIA calculates the proportions of those facets that influence the diamond’s face-up appearance. These proportions allow GIA to evaluate what the best cut for a diamond is, by studying how successfully a diamond interacts with light to create desirable visual effects, such as:

  • Brightness: Internal and external white light reflected from a diamond
  • Fire: The scattering of white light into all the colors of the rainbow
  • Scintillation: The amount of sparkle a diamond produces, and the pattern of light and dark areas caused by reflections within the diamond

This laboratory-grown diamond (left) and natural diamond (right) cannot be told apart using the unaided eye.

How are laboratory-grown diamonds made?

1. High Pressure, High Temperature(HPHT)With this method, laboratory-grown diamonds are produced using high-pressure, high-temperature conditions similar to what natural diamonds experience in the earth. HPHT diamond growth occurs at pressures of 5–6 GPa (roughly equivalent to the pressure exerted by a commercial jet airplane if balanced on the tip of a person’s finger) and at temperatures of 1300–1600°C.

2. Chemical Vapor Deposition(CVD)This technique enables scientists to grow laboratory-grown diamonds using moderate temperatures (700°C to 1300°C) and lower pressures. Carbon-containing gas is pumped into a vacuum chamber and deposits onto a diamond seed, crystallizing as laboratory-grown diamond. The eventual size of the diamond depends on the time allowed for growth.

How are laboratory-grown diamonds identified?

Laboratory-grown diamonds require advanced testing in a gemological laboratory to be identified with certainty. At laboratories like GIA, scientists and graders used sophisticated instruments to analyze diamond strain patterns, trace element composition, inclusions, fluorescence, phosphorescence and more in order to separate laboratory-grown diamonds from natural. These factors are different due to the vastly different formation conditions of laboratory-grown and natural diamonds.