Synthetic diamonds for use in jewellery exist and are quickly gaining in popularity [0]. If buying a diamond ring, you might want to get a synthetic one instead of a mined one [1].
Fwiw, my wife wanted a synthetic diamond and we found they were much more difficult to obtain in practice than was acknowledged. Like going to a listing of many many stones but they were all unavailable because they were out of stock or backordered or no one would ever respond. My sense at the time the supply and/or market were inflated to attract investors and maintain attention.
I do hope that's changed because we were really interested. But at the time it was a big mirage.
[0] https://en.wikipedia.org/wiki/Synthetic_diamond
[1] https://en.wikipedia.org/wiki/Blood_diamond