This may be a stupid question but, is there any method for determining how old a stone is?

First let me say, there are no stupid questions and the one you just asked is actually a good question. I am assuming you mean by age, how old the installation is and not how old the stone is. The stone itself is millions of years old.

There are several ways to tell how old the installation is. Record searches should be your first approach. How old is the building? If your dealing with a very old historical building you may want to check tax records, deeds etc. All these will give you a clue to the age of the stone. How thick is the stone? Prior to our modern cutting technology, stone was very thick, exceeding one inch in thickness. Do you know what kind of stone it is? If you do, chances are it’s not that old. The age of the installation is very important for several reasons. The age will tell you how well the stone is