My father was a diamond cutter (one of the folk who designed the modern “Portuguese cut” of the 70s) and he went through the evolution of diamond cutting from abrasion with copper disks (for cutting windows and facets) to laser cuts.

I distinctly remember going into the (then state-owned) workshops as a kid and watching the cutters at work with their loupes, and how they kept tabs on stones by checking in and out of the vaults little envelopes annotated with each step of the process - it was true craftsmanship.

Biggest stone I “saw” (they did resin molds of the large ones for senior cutters to measure and mark the places for clamping and cutting, and my father would bring some models home to study and review other cutters’ suggestions) was about 2x2x3cm, and IIRC it was cut down into many smaller ones due to impurities (you’d cut a window to peer in, assess where the impurities were and then plan the cuts to excise them or avoid including them into the finished cut).

The techniques are sure to be vastly different today, but the detachment with which he viewed his work was rather fun: they were intricate puzzles to maximize yield during the rough cut phase and reflectiveness during the shaping phase - they did the math by hand for the facet sizes and angles, and it took years to figure out the best ways to do some of the shaping in a reproducible fashion (that was his key achievement).

And all that time, they were “just pretty rocks”. He was very nonchalant about it, and never considered them of much value. DeBeers tried to hire him and he pretty much said he was done with the hype (rather amusing considering I’m about his age at the time and also fed up with our industry hype).

(Also, if you read Michael Crichton’s “Congo”, he got the diamond color names wrong)