There are none. Diamonds = crystallized carbon. Plain and simple.

Whether they come from the ground or from a machine.

(Need a second opinion? Here’s the FTC’s definitive stance via Forbes).

Lab grown diamonds evolve in laboratory conditions and a diamond can be grown in as little as 6 to 10 weeks.  These conditions replicate the natural growing environment of the Earth, so they are consistent with high temperature and high pressure.  The result is the same chemical and physical composition as a natural diamond. Each and every lab grown diamond is different with its own imperfections. Lab grown, man-made diamonds are inspected and certified with a clarity grade in the same exact way as a mined diamond.