Futurology

And even to this day we can’t synthesize large ‘jewelry’ grade diamonds.

Wikipedia says otherwise: https://en.wikipedia.org/wiki/Synthetic_diamond#Gemstones

Synthetic diamonds for use as gemstones are grown by HPHT or CVD methods, with the market share of synthetic jewelry-quality diamonds growing as advances in technology allow for larger higher-quality synthetic production on a more economical scale.

In April 2022, CNN Business reported that a synthetic one-carat round diamond commonly used in engagement rings was up to 73% cheaper than a natural diamond with the same features, and that the number of engagement rings featuring a synthetic or a lab grown diamond had increased 63% compared to the previous year, while the those sold with a natural diamond declined 25% in the same period.