I agree, one should be very careful in ascertaining the provenance of diamonds or not wear them.
Human trafficking is modern-day slavery through labor or commercial sexual exploitation in pornography and prostitution. Women and children are the most frequent victims.
Numerous studies paint the same picture. Demand is high and trafficking is very lucrative.
I think you misunderstand. Ascertaining where the diamonds come from doesn’t matter according to your argument. Anyone who consumes pornography is complicit in the slave trade, even if the porn that’s being consumed comes from a legit source.
This is the same of the diamond trade. It doesn’t matter that the diamonds you buy come from legit sources, it’s the fact that you’re buying diamonds at all that keeps demand high. There would be no desire for conflict diamonds if there was no desire for any diamonds. So consuming any diamonds, even legit ones, makes one complicit in the conflict diamond trade. At least, according to your argument against pornography.