I understand how you can think of it as a keyhole view. Instead, I think it's that I want "dense deposit" to mean something fixed, so we can look at a Roman go

I understand how you can think of it as a keyhole view. Instead, I think it's that I want "dense deposit" to mean something fixed, so we can look at a Roman gold extraction operation and say "yes, that is a dense deposit" or at a South African mine and say "no, that is not a dense deposit" independent of the technology in use. Here's a thought experiment for that research student - which would cost more using current wages: - extract 1 ton of gold from a deposit as rich as (say) the Dolaucothi Gold Mines when it used by the Romans, and using only Roman techniques. - extract 1 ton of gold from a deposit equivalent to a South African mine in 1900, using cyanidation techniques of that era. (I don't know if 1 ton is too low or too high to be reasonable.) > nuggets are no longer laying about to be picked up This isn't entirely true. People do still fund nuggets by happenstance. A news search finds things like https://www.yahoo.com/entertainment/family-finds-24k-gold-nugget-162757986.html https://www.yahoo.com/entertainment/family-finds-24k-gold-nu... from a few years ago. But yes, they aren't the types which kick of a new gold rush. In any case, Roman gold extraction wasn't just from picking up nuggets either, so I'm not sure that's quite the right comparison.