Niboy

i stumbled on a video on the internet (https://youtu.be/MBeMcgars_w), a stone that melts an iron nail in a few seconds. in another video, it showed there that the iron nail after being exposed to the stone/rock became very brittle. whats the explanation? please help. someone asked me this and i cant give an answer. thank you.

Someone asked me about this solvent but i dont exactly what it is. He showed some videos showing that this solution can brittle an iron nail in a few seconds. I wonder what kind of Chemical Solution is it. Can anyone help me about what is it and how its made? Thank you.