If I’m to understand mic_check_one_two@lemmy.dbzer0.com correctly, it’s something that’s:

Extremely hazardous,
non flamable, Extremely unstable, Reactive to water

And if ox means oxidising, reacts to exposure to oxigen.

I thought Lithium, but that catches fire and this is non-flammable.

I haven’t a clue what this could be, but now I’m curious.