Strange Behaviour

[kim03333]

i found some rocks/stones today that would look nice in my tank. i got them home, washed them and tested with vinegar. no fizzing or any kind of reaction so i thought they would be fine. next i wanted to boil them. didn't have a suitable pan so instead i put them in a bucket and poured boiling water - straight from the kettle into the bucket.

i heard a sound, sort of like one of the rocks had exploded, looked in the bucket and one of the rocks was producing tiny bubbles. there was a small flow, then nothing for about 2 seconds, and then another small flow. (this is while i'm waiting for kettle to reboil with another load of water). eventually the bubbles stop. then when i pour on more boiling water, the same thing happens again.

this rock looks different to the others it is pitted surface, whilst the others are smooth. i found them all in a salt water area (not the sea)

sorry for such a long description. if anyone can help me i would like to know what are the bubbles, are they a gas? why react in boiling water and not vinegar? and is is safe to use? many thanks, kim

 

[Mr Bliss]

i found some rocks/stones today that would look nice in my tank. i got them home, washed them and tested with vinegar. no fizzing or any kind of reaction so i thought they would be fine. next i wanted to boil them. didn't have a suitable pan so instead i put them in a bucket and poured boiling water - straight from the kettle into the bucket.

i heard a sound, sort of like one of the rocks had exploded, looked in the bucket and one of the rocks was producing tiny bubbles. there was a small flow, then nothing for about 2 seconds, and then another small flow. (this is while i'm waiting for kettle to reboil with another load of water). eventually the bubbles stop. then when i pour on more boiling water, the same thing happens again.

this rock looks different to the others it is pitted surface, whilst the others are smooth. i found them all in a salt water area (not the sea)

sorry for such a long description. if anyone can help me i would like to know what are the bubbles, are they a gas? why react in boiling water and not vinegar? and is is safe to use? many thanks, kim

Gas or liquid heated within pores inside the rock, and expanded, cracking the rock.

This is why boiling rocks is a bad idea. They can in fact explode.

 

[kim03333]

wow, i'm glad it didn't explode! i was under the impression that you had to boil the rocks. all the advice i found earlier today suggested to people that they boil them to kill anything b4 they go into the tank. well at least i will know for another time, and if i see anyone else asking on here about what to do with rocks i shall advise them what may happen. thank you for such a quick reply.

 

[Mr Bliss]

Yeah. It's a good idea to get rocks clean by thorough scrubbing (under warm water, no detergent), and you could treat them with bleach as well if you feel paranoid. Boiling them just seems like a bit of overkill in my opinion, although some people might disagree. I'm all for doing things "just to be safe" but I'm not putting my own health at risk just to remove a minimal risk of contamination.