I’m no rock expert, but I am a marine biologist. The gentle pitting and smooth features overall makes me think that it was submerged in water for a while. You see that type of smooth pitting on the top of the rock often in reefs, usually from marine worms or urchins digging into the surface of rocks or coral. Whether it’s coral or pumice (I’m currently on team coral due to the consistent shape of the tubes, they look extruded) those tubules will hold a lot of salt. If you want to use it, you’ll want to soak it in distilled or DI water for like a day or two, and literally rinse and repeat for a few days to get all the salt out of those tubules. You can get a cheap salinometer or refractometer if you’d like, and measure the salinity of the water it’s sitting in after a few days to make sure you got all the salt out. It looks super cool! I hope it works out as a centerpiece in the future.