Found rocks

So I was on the beach during my holiday, found some interesting rocks. I bleached them, scrubbed them, washed them, and so far the fish are ok, and levels in the tank are fine.

Of course I want to adjust slightly, so I go to take out one rock and put in a different one that I might like a little more ...only to find tiny bubbles escaping from the rock. I pulled it out immediately and it's currently soaking in another dish.

I've done the vinegar test, the rock is fine on that level. Any idea what caused the bubbles, and will it be ok to go back in the tank?

 

Is it a porous rock? It could just be air escaping.

 

Do we have any residents geologists who could identify rocks?



Pic 1 is in water, Pic 2 is out.

 

Both are a fish safe rock called gneiss.

 

The two pics are the same rock, in & out of water.
And what were the bubbles when it put it in the tank coming from the rock?

 

More than likely trapped air in a crack.

I sold rocks for 11 years and have kept gneiss in my tanks for my 30+ years of fishkeeping.

 

Thanks! Could I try and show you pics of some of the other rocks I found?

 

Sure!

 

Here we go, I've got a couple to share:

 

All found on the beaches of Cape Cod, MA.