Cleaning rock

[Spotted]

Ok, so I have a bunch of HUGE coral rock around my neighborhood right. I have found a few smaller pirces that have broken off. Is there any way to clean these for use in my tank?
The rocks have been exposed to the elements since like 1985.
Any help?

 

[mr_X]

I would not use local rock unless you know it's exact composition. Unwanted, and in some cases harmful minerals could leach out of the rock.