Some dangerous ground I tried working, it had fallen in from the surface in two claims and they found $18,000,000. I was hoping for a little by digging along the edge, but now I look back you are on opal or not.
I had put in hundreds of these props that are made of cypress and can hold 60 tonnes, some were needed and some not. You can get away with a lot in sandstone country, here you can see the hardwood capping bending to the weight. The trick is to put them in early before any movement starts, I had been down in claims where all the dirt is gone! Each prop about two feet apart and holding up 50 feet of over burden.
Near here some guys were working some very dangerous ground, as I talked with one of them in a drive some 50 feet back from the working face . The walls were pealing pieces off as we stood there chatting, each morning they had to clear the drive out from the night before. I'd thought I took some risks but these guys were at the limit for a few days, but were rewarded in the end.
There are safety courses now before you dig to help people understand the dangers involved, but greed is a powerful force.