Before we talk about how the lab-made rough diamonds are made, it is important to understand how the mined diamonds are formed. These processes are extremely similar-only one occurs naturally and the other occurs in the laboratory
Mined diamonds Geologists believe that diamonds were formed in the depths of the earth between 1 billion and 3 billion years ago. Although they don't know exactly how these diamonds were formed, they believe that the process started with carbon dioxide buried about 100 miles below the earth's surface.
Carbon dioxide is exposed to temperatures exceeding 2,200 degrees Fahrenheit and can withstand extreme pressures of approximately 727,000 pounds per square inch. Then, the diamonds are transported from the depths of the earth's core to the surface by deep volcanic eruptions.
Rough diamonds made in the laboratory The laboratory uses two processes to grow diamonds-high pressure high temperature (HPHT) and chemical vapor deposition (CVD).
HPHT diamonds are made using one of three manufacturing processes: belt press, cubic press, and split ball (BARS) press. All these processes create an environment of extremely high pressure and temperature conducive to diamond growth.
HPHT diamonds initially put a small diamond seed into the carbon. Using one of the above manufacturing processes, the seeds are exposed to a temperature of about 1500 degrees Celsius and pressurized to about 1.5 million pounds per square inch.
The pure carbon melts and begins to form diamonds around the starting seed. It is then carefully cooled to form pure carbon diamond.
CVD diamonds start with thin slices of diamond seeds, which are usually diamonds produced by HPHT. The diamond seeds are placed in a sealed room and heated to approximately 800 degrees Celsius.
The chamber is filled with carbon-rich gases such as methane and other gases. A technique similar to microwave or laser is used to ionize gas into plasma. Ionization breaks the molecular bonds in the gas, and pure carbon adheres to the diamond seeds and slowly crystallizes.
How are the lab-made diamonds rough certified and graded?
Lab-made diamonds are graded and certified using the same process as mined diamonds.
The diamonds are sent to a gem laboratory that specializes in grading diamonds. Most of these laboratories use 4c grading (cut, clarity, color, and carat-will be detailed later), but a few laboratories use their own standards.
The most popular diamond certification laboratories are:
Gemological Institute of America (GIA)
Antwerp World Diamond Center (AWDC)
American Gem Society (AGS)
International Gemological Institute (IGI)
Gemology International (GSI)
The diamond grading process of all diamond certification laboratories is roughly the same. Each diamond is independently graded by several gemologists in the laboratory. Summarize and analyze individual scores to determine the final score.
This process aims to provide a fair grade for each diamond. However, it is not uncommon for diamonds to receive different grades, not only from different laboratories, but also from the same laboratory if they are sent back for a second grading.
For this reason, there are many different opinions between consumers and diamond retailers as to which laboratory is the "best". However, it is important to remember that these opinions are completely subjective. Every laboratory, like everything in life, has its advantages and disadvantages.
Diamond retailers choose the laboratory they use because they believe that the laboratory can classify diamonds fairly. If diamond certification is an important factor in your purchase, you should talk frankly with your jeweler to understand which laboratory they use and why.
Most importantly, the jeweler wants you to be confident in your purchase, so don’t be afraid to ask questions in order to find the best lab-made diamonds for your engagement ring or jewelry.
Use 4c criteria to evaluate diamonds-cut, clarity, color and carat. Basically, they judge diamonds based on how well the diamond is cut from its original form into a gem, its flawlessness and clarity, and its size.
Below you will find a description of each category and the different measurements used for each category.