Re: Can you give me some info on rocks or minerals and dissolving of them?

Sounds like a fun project.  Rocks and or minerals that you might want to 
try dissolving are "limestone", "calcite (CaCO3)", or if you can find it 
"coquina" maybe even marble. These are rocks that are calcium carbonate 
based.  So in order to dissolve them you need to use a weak acid. Spring 
water dosent have enough of anything in it to dissolve rocks.  tonic water 
might not be much better.  Maybe try vinegar, or perhaps plain old rain 
(acid rain from polution).  As you said it must be a long term project as 
it will take a LONG time to dissolve rocks.  Just make sure that you weigh 
the rocks VERY accuratley  and several different times BEFORE and AFTER 
for each different solution. 

This is actually more chemistry than geology.

good luck