On the topic of the weird 'things' that you've seen and tried to burn with limited success; maybe you opened a portal playing with those high power lasers. I told you not to cross the beams! :tsk:
If that is copper, that almost certainly isn't corrosion. There are very few acids hat can disrupt the bonds of precious metals. The acids that can are EXTREMELY dangerous. Also, since the OP said the disturbance seems to move, that suggests an organic compound of some sort. Again, if that is metal, it wouldn't be any form of plant life. Also mention was a prism effect. That narrows the suspects down to a few rare earth metals. Is the object far heavier than its size would suggest? If so, beryllium is most likely. Densest metal known to man.
Beryllium (Be) is extremely lightweight and has a low density of 1.85 g/cm3.
The densest metal is Osmium at 22.59g/cm3.
I'd go back and re-look your periodic table of elements.
I'm pretty sure what I see here is some sort of salt crackle. If you heat salt(s) up hot enough they liquefy and and cause a crackle like this as they cool down.
Hydroxides (esp.) Sodium and Potassium Hydroxide can do this at lower temperatures, relatively speaking.
Another possibility is a partially cured / scorched alumina thermal epoxy..
There's more to this story I think. :thinking: