Primary v's Secondary deposits

While there has been plenty of discussion around the differences in what is recovered from a primary deposit v's a secondary deposit, I haven't seen much talk about the practical differences in mining.

In a primary deposit, the stones are still embedded in the host rock and need to be extracted from there, while in a secondary deposit the stones have been freed from the host rock by erosion and are sitting loose among the gravel in ancient river beds. It stands to reason that there must be some significant differences in the recovery process, costs involved etc.

Can anyone provide some detail around this? GEM are mining both primary and secondary deposits. Does anyone know how they manage these two different sources?

@Cralo @hardrock anyone else?