The history of the Diggers Graveyard mine isn’t at all clear. We don’t know when it was first worked, or even if it was profitable. There’s no doubt, though, that some effort was gone to to find and extract the gold. As well as the diggings at the edge of the river, there are a few pits which may just have been test pits, or, maybe, the beginnings of exploratory shafts.
It’s difficult to illustrate here in a 2-dimensional form, but the dark patch in the centre of the photograph is such a pit or filled-in shaft.