The company which had exploration rights (1600acres from memory) in the 90's used backhoes etc.
I fired off letters to the department which I think (hope) were influential in having the permits cancelled.
At least that is what their replies indicated.
My mate, who was one of the old timers, reckoned the area of and around Sapphire Bend was a crater lake remnant of a volcano. His theory was based on the regular ripples in the floor of the wash band. There are places where several wash bands at depth separated by fine sediments can be identified.
We dug quite a few holes like the one shown, but we always backfilled. My old mate was like a human backhoe, a test hole like that we (mainly he) would dig in 2 days.
There are open holes like that around Chain of Ponds, my dog fell in one, took ages to find her, the only time she lost her voice!
Although I now live around Glen Innes, I have never seen stone to rival the blues from the Black Springs area.
Mike