Synthetic or lab-grown diamonds are a smart alternative to natural diamonds for jewelry, plus they have many commercial uses. Both natural and lab-grown diamonds are crystals of pure carbon. In contrast, a diamond simulant (e.g., cubic zirconia, strontium titanate) is not carbon and lacks the chemical and physical properties of diamond.
What Is a Lab-Grown Diamond?
As the name suggests, a lab-grown diamond is a diamond that is created in a laboratory instead of being formed naturally in the Earth’s mantle. These diamonds are made using various techniques that mimic the high-pressure and high-temperature conditions that occur naturally in the Earth’s mantle, where diamonds are formed. Synthetic and natural diamonds have the same hardness, luster, dispersion, and colors. The big difference is how long ago they formed. Plus, scientists control the chemistry and conditions in a lab. So, some lab-grown diamonds are very much like natural stones, while other synthetic diamonds display novel properties.
Researchers discovered that diamonds are pure carbon in 1797. James Ballantyne Hannay (1879) and Henry Moisson (1893) had early successes in making synthetic diamonds by heating charcoal with iron within carbon crucible. Immersing the heated crucible in water solidified the iron, presumably generating enough pressure to compress the carbon into diamond. But, other scientists were unable to replicate Hannay’s and Moisson’s results.
The first verified lab-grown diamonds were produced in 1953 by ASEA in Sweden using a process called high-pressure, high-temperature (HPHT) synthesis. This process involves subjecting graphite to high pressures and temperatures to convert it into diamond. Since then, several other methods have been developed to create lab-grown diamonds.
How Lab-Grown Diamonds Are Made
The two most common processes for making lab-grown diamonds are HPHT synthesis and CVD. However, there are other methods, too.
- High-Pressure, High-Temperature (HPHT) Synthesis: This method uses a press to apply high pressures and temperatures to graphite (a carbon allotrope), which converts it into diamond. The diamond is then cut and polished into the desired shape.
- Chemical Vapor Deposition (CVD): This method involves heating a substrate material (usually a thin slice of diamond) in a vacuum chamber and introducing a gas mixture containing carbon. Methane (CH4) is a common carbon source. The carbon atoms settle onto the substrate, forming diamond crystals.
- Microwave Plasma Chemical Vapor Deposition (MPCVD): This method uses microwaves for heating the substrate material. The vaporized substrate forms a plasma that contains carbon. The carbon atoms then settle onto the substrate, forming diamond crystals.
- Detonation: Detonation nanodiamonds form when carbon-rich compounds explode within a metal chamber. The explosion is the source of the high temperature and pressure that forces the carbon atoms into a crystal structure. The resulting powder of tiny diamond crystals finds use as a polishing material.
- Ultrasound Cavitation: In this process, ultrasonic cavitation forms crystals out of a suspension of graphite in an organic liquid. While the method is simple and cost-effective, the resulting diamonds tend to be imperfect. So, this method requires optimization.
Advantages of Lab-Grown Diamonds
Lab-grown diamonds have the same chemical and physical properties as natural diamonds. They are both pure carbon and have the same crystal structure. However, natural diamonds vary widely in quality, while lab-grown diamonds have consistent and customizable properties, depending on the materials and method used to create them.
Here are some of the advantages of synthetic diamonds over natural diamonds.
- They take much less time to form!
- Their properties are customizable.
- Lab-grown diamonds are often less expensive than natural diamonds.
- Lab-grown diamonds are considered to be more environmentally-friendly and ethical because they do not involve mining and are not associated with human rights abuses.
Uses of Synthetic Diamonds
Lab-grown diamonds have a variety of uses, including in jewelry, cutting tools, and scientific research. The use depends on the properties of the crystal. Diamond is very hard, has high optical dispersion, is chemically stable, and is an electrical insulator while being an exceptional thermal conductor. In jewelry, lab-grown diamonds are an affordable alternative to natural diamonds. In cutting tools, lab-grown diamonds are extremely hard and durable. For scientific research, lab-grown diamonds find use in experiments that require extreme pressure and temperature conditions. Boron-doped synthetic diamonds are superconductors. Other uses of synthetic diamonds are for infrared windows, synchrotron radiation sources, diodes, and switches.
How to Tell Natural and Synthetic Diamonds Apart
You can’t tell natural and lab-grown diamonds apart with the naked eye. They have the same chemical and physical properties and come in all the colors of natural and color-treated natural diamonds. Both types of diamonds sparkle equally well. However, there are some potential identifiers.
- Inscription: Some lab-grown diamonds carry an inscription with a unique serial number or symbol that identifies them as lab-grown. Find this inscription on the girdle of the diamond, which is the thin edge that separates the top and bottom of the diamond.
- Inclusions: Inclusions are small imperfections that are present in most natural diamonds. These can include cracks, clouds, and other minerals that have become trapped inside the diamond. Lab-grown diamonds are usually free of inclusions or have fewer/different inclusions than natural diamonds. For example, metallic inclusions occur in some synthetic stones, but not in natural stones.
- Chemical Composition: Most natural diamonds contain some nitrogen, while most synthetic diamonds are free of this impurity.
- UV Fluorescence: Some natural diamonds (about 30%) fluoresce under ultraviolet light, usually emitting a blue glow. Less often, diamonds glow white, red, purple, green, orange, or yellow. Lab-grown diamonds do not usually fluoresce or emit a different color under ultraviolet light. However, a small percentage of synthetic diamonds receive treatment so that they fluoresce just like natural stones. In either case, fluorescence usually arises from traces of boron, nitrogen, or aluminum. Lab-grown diamonds undergo heat treatment and irradiation to enhance color and fluorescence.
- Price: While lab-grown diamonds are becoming more popular, they are often less expensive than natural diamonds. If a diamond is a significantly lower price than similar natural diamonds, it is likely lab-grown. That being said, the four C’s (cut, color, clarity, carat weight) play a bigger role in pricing than whether a stone is natural or synthetic.
- Hannay, J. B. (1879). “On the Artificial Formation of the Diamond”. Proc. R. Soc. Lond. 30 (200–205): 450–461. doi:10.1098/rspl.1879.0144
- Moissan, Henri (1894). “Nouvelles expériences sur la reproduction du diamant“. Comptes Rendus. 118: 320–326.
- Railkar, T. A.; Kang, W. P.; Windischmann, Henry; Malshe, A. P.; Naseem, H. A.; Davidson, J. L.; Brown, W. D. (2000). “A critical review of chemical vapor-deposited (CVD) diamond for electronic applications”. Critical Reviews in Solid State and Materials Sciences. 25 (3): 163–277. doi:10.1080/10408430008951119
- Tennant, Smithson (1797). “On the nature of the diamond”. Philosophical Transactions of the Royal Society of London. 87: 123–127. doi:10.1098/rstl.1797.0005