Well, I am doing a science project and my topic is "Which type of rock(from the selected) dissolves faster. I'm doing it on 3 or 4 rocks but I don't know any rocks that dissolve fast. Google is useless and I need them to continue my project. I already chosen Granite as my first rock and I need about 2 or 3 rocks. I need a rock that can dissolve in about a month or so. It dosn't have to dissolve completely but just a little bit. Can some one please help me?