Most of the aluminum cases are Berdan primed (if you look down into the case, you'll see two off-center flash holes, instead of one in the center. You can decap them, but it's a right pain to do so. (As an experiment once upon a time, a buddy and I used transmission fluid and a close fitting piece of dowel rod to decap some aluminum cases. Simply fill the case half full of fluid, stick the dowel down the case mouth, and smack it with a small dead blow hammer. It worked, for given values of "worked", but was messy and time-consuming, and the primers were an odd size, anyway. And did I mention it was really messy?)
So, unless you can use it for jewelry, picking up aluminum or steel cases is good exercise, and a nice bit of clean up at the range.