No-one keeps cores because water bores are usually percussion...

No-one keeps cores because water bores are usually percussion hammer drilled, but if you drive out there you will often still find the cuttings/chips around the drill hole collar if you are lucky, occasionally the local farmer also keeps some drill cuttings (also if you are lucky). If you don't go out there you will never know. There might also be some historic exploration drill hole cuttings and core stored at the relevant state core library/dept of mines but you would have to be lucky for the few reference holes to fall within your own exploration tenement, again, you never know if you never go.