Two Paths to a Diamond
Infographic by Daisy Fregoso
These articles are not intended to serve as medical advice. If you have specific medical concerns, please reach out to your provider.
The oldest natural diamonds out there are roughly 3.3 billion years old, but lab-grown diamonds did not come around until the 1950s. Today, the lab-grown diamond market has expanded rapidly with these stones costing roughly 30-40% as much as their natural counterparts.
So, what are the chemical and structural differences between natural and lab-grown diamonds? Surprisingly, there are very few. Both are made up of only carbon, each containing four covalent bonds and a tetrahedral structure, where each carbon has four covalent bonds at a bond angle of 109.5°. This sp3 bonding is what gives the diamonds their characteristic hardness. - A 10 on the Mohs hardness scale, along with a density of 3.5 g/cm3 and a refractive index of roughly 2.42, produces the brilliance. Structurally and chemically, both types of diamonds are considered diamonds.
The primary difference between the two types of diamonds lie in growth patterns and inclusions. Natural diamonds are actually a little less pure, as the conditions that formed them fluctuated over the years, leading to an irregular and complex growth pattern. Lab diamonds, on the other hand, are made in a very controlled environment, leading to more uniform growth zones.
The types of inclusions in diamonds vary as well. Natural diamonds tend to contain mantle minerals such as garnet or olivine, while lab-grown diamonds may contain inclusions from catalysts used and potential graphite that may have entered the stone. Natural diamonds also tend to have a light yellow tint, which is caused by the levels of nitrogen within them. This is not the case with lab-grown diamonds, as nitrogen levels are controlled throughout their creation. All in all, most people, including trained jewelers, are usually unable to distinguish between natural and lab-grown diamonds without specialized equipment. The differences between the two types of stones are extremely subtle and microscopic.
If there are so few structural differences between these two types of diamonds, why are they priced so differently? Although there are very few structural differences in the diamonds themselves, the answer lies in how the two stones are formed. Natural diamonds were formed roughly 3 billion years ago, 150-200km beneath the Earth’s surface. Deep down, the average temperature is 900-1300 degrees Celsius. The diamonds are carried to the surface of the earth by rapidly expanding magma through volcanic eruptions that form kimberlite pipes. The magma eruptions that carry these diamonds to the surface are extremely rare, and only 1 in every 200 of them even contain gem-quality stones.
Lab-grown diamonds are made using two methods. The first method is high-pressure high-temperature, or HPHT, technology, and the second method is chemical vapor deposition, or CVD. HPHT diamonds are made over the course of a few days to a few weeks, from a metal solvent-catalyst, at temperatures of roughly 1300-1500 degrees Celsius and a pressure of roughly 5-6GPa. The biggest flaw of HPHT diamonds is that they can contain metallic inclusions from the catalyst used. CVD diamonds are made by taking a thin diamond seed and having carbon atoms deposit layer by layer onto this seed. This method uses a mixture of methane and hydrogen gas, with a temperature of 800-1200 degrees Celsius. These diamonds tend to grow at a rate of roughly 0.1-0.3 mm per day. CVD diamonds often show layered growth patterns when looked at under magnification.
Although the methods to create diamonds can vary greatly, the qualities of the stones themselves are very similar. Whether one wishes to purchase a natural or lab-grown diamond is up to the consumer and what matters most to them.