How do you know when it's safe to tunnel without framing, or bolts? My mines are in decayed granitic rock, with the Au in quartz stringers. The rock could be worked with a rotohammer and a chiselbit, though slowly, of course. I have not worked either of them yet, having only filed on these old mines this year. They date from the 1860-90s. Also, which is more cost-effective; bolts or timber framing? Thanks again!

Thats what i use in my mines, a Bosch hammerdrill (one of the bigger ones) along with a good selection chisel bits(wide,narrow and bullpoints) and rock bits. My bits are from 18" up to nearly 3 feet long (usable lengths). They work VERY well in broken and cracked formations like is in my mines. Id say if you dont want to frame COMPLETELY then at least timber it with stulls. The mine ive been sinking a shaft in i re-timbered about 10 feet down from the collar and just stulled the rest of the way down even though the rock is very hard. The shaft originally was only 14 ft deep but now ive got it over 50.... and just by drilling it with my hammerdrill and blasting it with the substitute powder. The shaft was orginally started in a fault inside a mountain with a quartz footwall and a granite-niess hanging wall but the gold was located in the filler rock BETWEEN the foot wall and hanging wall.. LUCKILY most of the fill rock in the fault is mainly broken so i can blast it easily.

As far as my opinion goes on the cost effectiveness between timbering and roof bolts, id say the wood timbering is a bit cheaper since you would need to drill holes in order to drive in the roof bolts. Also, if im thinking right, i believe using roof bolts requires special equipment (drivers, bits, etc). The only rock bolting i do in my mines is when im attaching my ladders to the rock, in which i will drive the long lag bolts through the rungs(through pre-drilled holes of course) of the ladders(the top and bottom front sides) and then drive the bolts into the footwall by way of holes i had previously drilled for the bolts, THEN in order to keep the bolts tight and before i drive the bolts in i will mix a small batch of quick cement to put in the drilled hole then drive the bolts. That fills up any cracks or whatever that might keep the bolts from staying tight. Once all of that is finished then i will strap the ladders together end to end. I only do this method because i dont bother with the timbering of the shaft all the way down, just the stulling.

What do you mean? why would you re open a mine from the 1800s? Is it just a hobby to mine the iron, or are you actually going to make small amounts of steel with it? I sounds like that would be a neat idea if you are a blacksmith and you use the iron that you mine yourself!

Dave,
Wallrat is talking about mining Gold (au) in Quartz.

Chris
in New Zealand

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