Learning

CVD stands for chemical vapor deposition.
  Lab grown diamond seeds are loaded into a CVD reactor. Then, a mix of gasses containing carbon is added at a very low pressure. Microwaves are added to heat the gases and generate a plasma. When the temperatures climb over several thousand degrees, the gas molecules break apart and carbon atoms bond to the seeds, growing them one layer at a time.

While they may look similar, diamond simulants (like cubic zirconia) are chemically not diamonds at all. They’re completely different gems and materials. On the other hand, lab-grown diamonds are chemically the same as natural diamonds, but their creation process is sped up by science.
What is a simulated diamond?
Diamond simulants and lab-created diamonds often get mixed up, but they’re completely different. A diamond simulant is not a diamond at all, because the chemical properties are completely different. They can be made out of anything from glass to cubic zirconia. While they may look similar at first, diamond simulants aren’t as hard and don’t have the same optical properties as diamonds, so they’ll show signs of wear and won’t be as sparkly.
Lab-grown diamonds vs. Cubic zirconia
Cubic zirconia was created to be a less expensive alternative to diamonds. It’s chemically completely different, not as hard and lacks the same sparkle. It’s also not considered a gemstone because it can’t be found in nature. It’s made from powdered zirconium and zirconium dioxide, melted together and formed into a stone.
Lab-grown diamonds vs. Moissanite
Moissanite is a completely different gem, that tends to be less expensive than a diamond. It started out as a naturally occurring mineral, but natural supply wasn’t enough to make even the smallest pieces of jewelry. Scientists then found a way to replicate it in a lab to make it commercially available. While it might look like diamond it’s a much lower grade on color and hardness.