soaking natural rocks for chemical leach???

[huma-huma]

I have found some natural rocks nearby, and was wondering if I should soak them to rid them of any possible harmful chemicals? They look decently clean and were not covered in any liquids...I know that people who diy caves and backgrounds usually soak them to leach away bad chemicals, any suggestions?? Ohh and im using these rocks to build rock formations in my tank...

 

[jcolon]

I usually boil rocks I find for a few minutes. The issue is what types of rocks? Granites, quartz stones and slates I find to be aquarium safe and ok to boil. Stay away from limestones, marbles (raise your pH) shales and sandstones.