there are 3 variants to warpstone. Stable, Weak, and Unstable.
Stable warpstone (WARPSTONE_SOLID in the raws) leaves a boulder behind that can be used for a few tech related purposes.
Weak Warpstone (WARPSTONE_STABLE in the raws) Evaporates on mining, and the miner that hits it, is afflicted with a MINOR syndrome. They get dizzy, and slow, for a few days, and generally be less efficient. BUT it is not debilitating, just annoying.
That leaves us with ...
Unstable Warpstone (WARPSTONE_UNSTABLE in the raws). This stuff is NASTY, and it WILL kill your miners. Think, Ebola. In rock form. Released as a breathable gas, upon getting struck by a pick. Not a pleasant death either.
To the OP, it sounds like both of your miners got hit by unstable warpstone.
There are a few ways to avoid this very nasty death.
1) and easiest, Turn harder mining OFF
2) only use MASONS GUILD dwarves for mining. They are immune to the nasty. It will still slow them down, but only about on par with weak warpstone on a normal dwarf
3) use 'digv' when mining warpstone. It will NOT "dig" the unstable, only the weak. You can later go back, and manually dig the Stable warpstone (gotta get the good stuff =P)
4) use DFHACK changevein to change all the weak stuff to stable, and especially change the unstable to stable or weak.
5) use dfhack reveal, to check out a vein of warpstone to see if there is any unstable in an area you are planning on digging out for various uses.
and finally
6) (my favorite, as well as many others) Dont have miners doing ANYTHING but mining, and just dont care when they die. Your coffin industry will be booming. Between coal dust, and warpstone, you will go through at least 5 - 10 miners a year. Dont like a specific dorf? Stick em in the mining crew. Using the mining crew as a death sentence. You just have to remember that all dorfs are expendable. If you have gold flowing out your ears, you can use the guild hall to change some of your miners into masons guild. In past versions masons guild had a few problems and wouldnt properly convert. I dont know if meph has fixed it yet.
