As I understand, the diamonds in diamond hones and pastes are man-made. Both DuPont and General Electric have proprietary methods of manufacturing artificial diamonds (that aren't jewelery quality, just hard like the real thing) that are used for grinding, honing, polishing of real diamonds, carbide tools, and sometimes our razors.

Bench hones are generally made from monocrystalline diamonds, made by G.E. which are more expensive to make, but do not break down, thus making a consistent sharpening surface.

Lapping pastes are generally made from DuPont's polycrystalline diamonds, which do fracture into ever finer grit diamond shards as they are used, thus producing a very fast and fine polishing compound.

So diamond hones (the majority of those readily available, that is) would be man-made. You may be able to find natural diamond dust hones, but I think manufacturers would hype the HELL out of them, and jack the prices up substantially.