1. Manmade compressed and heated carbon is as passable to the next generation as the geologic kind. What is the issue here exactly? If anything its more awesome we can make our own and not rely on geological processes.

2. Why do I need to insure carbon? Its... carbon, super abundant, element 6. Present after the first generation of stars exploded in the universe. Are you investing in diamonds? They almost never go up in price, try reselling one or look at resale value before you worry about insurance.

3. What is the goal of this question? To show the Jones' that you have too much money and can pay the danegeld for authenticity? Before the 1940's diamonds weren't even a thing in marriage. If you could reproduce the Mona Lisa perfectly, would you pay N times as much for the original? Even if it was impossible to tell? Why is that so important?

4. Diamonds are already used for industrial uses, their "rarity" (they're not rare) is all due to a cartel named de beers controlling supply. They're common as hell, as noted, they're just compressed and heated carbon. These industrial uses are why we have these manmade diamonds in the first place. They're better than the originals as they're more consistent without imperfections. Just like modern steel would produce a katana infinitely better than folded crappy steel that the originals were trying to overcome.