I'm pretty sure you can, though I wouldn't if it means a lot to you. If the TSA agent does not like it, they will make you leave it behind. Leave it on top of your bag, and have a good reason for it. It will definetely get their attention when they x-ray it.
I brought back a coconut-sized chunk of the Roman wall from England, and the Heathrow security chap said "whut the bloody ell is this" I considered saying it was a looted national treasure, but I just told him I collect rocks.
I also brought back a duffel bag full of petrified wood from someplace in the desert. The only one who freaked out was the flight attendant. She said it was bad luck. Sure enough, I got furloughed 6 years later.
This was pre 9-11 so YMMV.
btw, Mag Lights are allowed, at least to the 3 cell size.