Unfortunately, De Beers controls the natural diamond supply, and they leave much to be desired in corporate ethics.

https://en.m.wikipedia.org/wiki/De_Beers#Legal_issues

And the US holds 50-70% of the total world market capitalization, and yet here we are.

Believe 15A and 19A as much as you can believe De Beers' 'Building Forever 2030 Goal's