Who said anything about slavery? The vast majority of third world workers mining diamonds do so in the regulated commercial sector. These are largely technical engineering jobs that bring investment in infrastructure into the country, certainly much more so than many other local opportunities. A single mine like those in Botswana can employ thousands of people, and be the core of the local economy. I'm not saying there are no slaves in diamond mines, but if so it's a marginal source.

Oh my good grief. What on earth did you think I was advocating?