Ooooh! I know what this means! Dwarves will cancel digging for two reasons: the stone is wet (which means that, right behind it, there's a large body of water) or when the stone is warm. That means magma. And magma is an even better fuel source than coal. It's the most efficient fuel source in the game. With a little careful digging, I found a vast underground sea of magma. Now all I need is some metal! And usually, when you find magma, you find something far better than iron.
Anyone reading this a Lord of the Rings fan? Of course you are, that's a stupid question. In Dwarf Fortress, adamantine is pretty much the same as mithril. Far, far, far more valuable than gold, and by far the strongest and lightest metal in the game. An army in full adamantine armor wouldn't need to be any good at combat. They'd be nigh-invulnerable. Adamantine is bad for hammers and maces (sorry, Solon!) since it's so lightweight - it'd be the same as wielding a hammer made out of styrofoam - but the swords and spears would be legendary.
There's a catch to adamantine, though. It comes in tubes, and these tubes travel all the way down to... well, I won't say. I'll save that surprise for later. The catch is to mine just the outside of the adamantine. You don't want to pierce that tunnel and find out what's inside. It's a risk, but too juicy to ignore. I want that adamantine. So I set my miners to very, very delicately peeling away a few layers of the precious metal.
To do this, I would carve out small sections by digging channels. That means I would start at the level above the adamantine and dig down. If I ever accidentally pierced the warm stone, the magma would safely flood the lower level. This kept my dwarves safe as long as they stayed on the floor above. Of course, one of my dumb dwarves fell in.
You're surrounded by liquid hot lava. Why didn't you have an exit plan?
The bad news is that Olon the Miner melted to death. I do mean that literally - it's not like she died and then her corpse melted away. Her body melted, and then said "fuck it," and stopped living. That's the bad news. The good news is that she didn't take her mining pick with her.
Jesus, she was pregnant, too? That's dipping into some serious black comedy. Wonder if Udib'll make a statue?