And that limits a miner to 133 large ore or 800 small ore in the packy, and 30-40 ore on them, for a total of 350-450 ingots from a mining trip, compared to taking a fire beetle with them, and being able to mine 4000-5000 ingots in one trip. (not to mention being able to send iron ingots to the bank 1500-2500 at a time with one charge from a bag of sending, as opposed to sending at best 40 or so ore with one charge, to stay out longer).
Lord Frodo is correct.
Zalan, AT BEST, it might be useful for someone using the new "mine only stone" setting in Fel, needing protection. It's worthless for anyone mining anything else.