The first synthetic diamonds were produced by General Electric in 1954. A synthetic diamond is basically a rock that has the durability, refractive index & hardness of a natural diamond - but it is made by man. A synthetic diamond should not be confused with stimulant diamonds, such as glass, cubic zirconia, or moissanite.
Although the technology for synthetic diamonds came into play in 1954, no synthetic diamonds were ever seen on the market until the 1990's. This was due to the fact that it took many years for General Electric to produce a synthetic diamond that could compare with the quality of a natural diamond - and when they figured out how to do it, they found that it cost more to produce a synthetic diamond than it did to mine and cut natural diamonds.
Finally, a small company by the name of Gemesis Corporation figured out a way to produce synthetic diamonds that were of the same quality as natural diamonds, at a cheaper price. Today, Gemesis produces synthetic white diamonds, and colored diamonds as well. These diamonds sell for about 1/three of the cost of a natural diamond, but there is a shortage of them, and they are hard to find. In fact, it seems that synthetic diamonds are rarer than natural diamonds!