ok.. first
weary = tired or worn out.
wary = cautious
second, other than some rocks possibly adding hardness to the water, there is little damage that the rocks can do. i have lots of native and not so native rocks from the natural environment. if i'm worried that the evil 2-legged folks have put some kind of chemicals in them or on them i boil them and/or bake them in the oven at 400 degrees F. (and let them cool) before i put them in my aquariums.
i do not use them if they may have a hollow center, as in a geode. or rocks that i can break with my hands, like clay. i do use kiln dried clay and terra cotta pots as decorations though, but the key here is the kiln dried. depending on the material in the kiln and the desired effects, temps in kilns go over 1000 degrees F.