Hi Neil,
No I don't think Geoscience Aus is wrong, its just one of those names that crop up all over the place. Lots of my ancestors were born, lived and died at places that just don't exist any more, temporary hives of activity given a name, then abandoned. Mosquito, Browns, Italian Gully, Jones Creek, Hiscocks, Gumtree, Chapel Flat, I have Great (great) Grandparents born in all of these ex places and I have tracked them all down, some are easy, Italian gully is on good modern maps but you would struggle to find some of the others.
From those mining reports on Trove it appears Hard Hills was a very short lived rush, quite a few reports of mines being worked out.
Andy and Stuart
The Mines Library and State Library are certainly on my list to visit when I am in melbourne next time, as is the Ballarat Library collection, probably the Buninyong Historical society will be first as I am visiting family there in the next week or so, as long as I can arrange the visit to coincide with open day at the society.
Thanks all for your input. Now for some legwork.