While I was recently in Arusha, Tanzania, I sat down with Salim, an experienced gem trader and gemmologist, to talk about what years of working inside the gemstone market had taught him about buying high-value gemstones.

A large piece of rough does not necessarily produce a large finished stone. And a beautiful-looking piece of rough does not automatically contain a beautiful cut gemstone. The important question is not simply: What does this rough weigh? It is: What can realistically be recovered from it?

A laboratory report can tell you what a gemstone is, but not the full story of how it reached you. Drawing on conversations across East Africa’s gem trade, I explore the hidden human risks behind high-value gemstone purchases.