Diamonds: Man-made & Enhanced
There are two methods to create synthetic gem-grade diamonds. The first is high pressure high temperature or HPHT. A diamond seed is placed into a specialized press along with a high purity carbon source. The chamber of the press is then brought up to the same pressure and temperature as the same environment diamonds are created in the earth’s mantle. This method is the cheaper of the two as it requires less precision and preparation of materials.
The second method is carbon vapor deposition or CVD. It is a much more complicated process and makes use of incredibly complex chemical reactions. In very simple terms, it is similar to making your own rock candy where sugar crystals form onto a skewer when it’s submerged in a hot, sugar rich solution and left to cool. This method is more time consuming and expensive but it’s more flexible and can be adjusted to fine tune the final product. Another advantage is CVD machines can create much larger diamonds than those created through HPHT.
Identifying a lab made stone is an extremely difficult task. The Gemological Institute of America is constantly creating and refining tests to differentiate lab made and natural stones. One method is to view the diamond’s crystal growth pattern under strong magnification and specific lighting conditions. Natural diamonds will show a concentric pattern as heat and pressure are applied uniformly from all directions. HPHT diamonds will display a cross shaped pattern as the presses exert pressure from a discernible number of directions. CVD diamonds are grown vertically, layer by layer, so they will display regular striations throughout.
Diamonds, whether they’re natural or man-made, won’t be perfect. It’s expected that they’ll have inclusions of some sort or they won’t be perfectly colorless. Creating diamonds from scratch is possible so it’s no surprise enhancing a diamond is entirely possible as well. To remove black inclusions, a laser is used to drill down to the offending inclusion. Once there is a clear path to the inclusion, the diamond is soaked in acid to dissolve the amorphous carbon away. These laser drilled holes are invisible to the naked eye but can be viewed using a jeweler’s loupe. Some companies who enhance diamonds will be kind enough to engrave their diamonds as such. Below is an image of a clarity enhanced diamond under magnification. It shows the telltale vertical drill marks and on one of the facets, you can barely make out a 'CE' inscription marking it as clarity enhanced.
Another method used to enhance diamonds is fracture filling. Laser drilling is used to gain access to unwanted fractures within the diamond. The fractures are then filled with a solution that closely matches the diamond’s refractive index. Fracture filling can be detected more easily than laser drilling. The telltale sign is random flashes of light appearing that don’t correspond to any facet when rotating the diamond.
Another characteristic of a diamond that can be enhanced is the color. The ideal diamond is completely colorless but most diamonds are going to have a touch of some color, usually yellow or brown. To permanently change the color of a diamond, either irradiation or high pressure high temperature (HPHT) treatments are used. While diamonds are preferably white and colorless, irradiating diamonds can be requested to impart a bold, vibrant color. During the first step of irradiation, the diamond will be either green, blue, or black on the surface. Further annealing treatments are used to further change the color of the stone to yellow, orange, brown, or even pink. To remove color from a stone and push it higher up the color scale, HPHT is commonly used. This process works best with brown diamonds. Depending on the nature of a diamond’s coloration, HPHT treatment can also be used to intensify the color of yellow diamonds.
Hopefully you learned something you didn't know about man-made or enhanced diamonds. It's important to remember that just because a diamond is created or enhanced by a machine, it doesn't make it any less of a diamond. It loses a significant portion of its value, but in every sense, it is still a diamond. A diamond is cluster of carbon whose crystal structure is diamond cubic. That's it, there's no requirement beyond how the carbon atoms have arranged themselves.
That said, there is a reason why people would choose to purchase a man-made or enhanced diamond. In the case of man-made diamonds, there might be minor savings or a moral obligation felt by the purchaser to avoid purchasing a mined diamond. A few decades ago, conflict diamonds were a major issue but with the introduction of the Kimberley Process, the problem has been all but eradicated. The Kimberley process essentially ensures that the entire diamond supply chain is run through proper channels and not exploiting anybody's labor. From the miner to the cutter to the setter to the retail store to the end customer, everyone involved is only involved in transacting with businesses who are certified as legitimate, conflict free, sources.
What might drive a person to purchase an enhanced diamond is much simpler than for a man-made diamond. In these instances, it usually comes down to price. A huge draw of diamonds is their natural beauty. From finding the diamond all the way through the typical stone cutting process, countless steps are taken to maximize the quality of the diamond at the end. Flaws like inclusions and coloring add to the character of the diamond and enhancements like fracture filling ruin the natural beauty of a diamond by affecting the inside of it.