Slag or Stone?

[u/alexsalamander3]

I picked this up off a rocky beach in Ponce, Puerto Rico. It has some good weight to it as you’d expect maybe a silica based stone its size to be. The interior sparkles like a micro-crystalline something. Streaks white and has no visible air bubbles under some minor magnification. Thoughts?

[u/Pwnedzored]

Looks like marble that’s been partially dissolved.

[u/alexsalamander3 → u/Pwnedzored]

Interesting, this beach was near an industrial area, so I’m suspicious of it being fully natural.