What if someone could cheaply produce perfect, synthetic diamonds, indistinguishable from the natural ones?

at the current time, the world market is flooded with natural diamond product. there are a number of Kimberlite deposits in the US that would be commercial, if there was a guarantee of good price. the age of the deBeers monopoly in market is over. because of blood diamonds, they have even fallen out of favor for prestiege purposes, like wedding rings. My uncle had a method of diamond production and no one offered to harm him.