Per the chart at Depths of materials?, you don’t want to dig down to mantle. Instead I’d suggest tunneling at depth 10-11 and digging up for them. Or depth 15 and dig down to 10.
Per the chart at Depths of materials?, you don’t want to dig down to mantle. Instead I’d suggest tunneling at depth 10-11 and digging up for them. Or depth 15 and dig down to 10.