A bookkeeper does the counting for you on the stocks screen.
But anyway, here's a trick that might let you make the item easily...
First, find some un-mined granite somewhere. If you can find it along the outer cliff, that'll make this even easier.
Mine it.
Build a craftdwarf's workshop or a mason's workshop right next to the newly-mined chunk of stone.
Define a 1x1 stone stockpile directly under said chunk of stone.
Now have the workshop right next to it make something using rock. It should grab the closest piece of rock from a stockpile, which will definitely be your newly-mined granite.
Of course, you don't even need to newly-mine the granite to do this... you can just build a workshop adjacent to one of your already-mined pieces. But those are probably in the middle of lots of other stone, making it harder.
Or you could just undefine all your stone and mining stockpiles everywhere, if you have any, and then define a single 1x1 stone stockpile under an existing piece of granite. Dwarves will always take from a stockpile first if one exists, so with your only stone or ore stockpile being a 1x1 thingy holding just one piece of granite, you've guaranteed that the next stone thing you make will be granite in composition, no matter where your workshop is.
[ August 27, 2006: Message edited by: Aquillion ]