Place/attraction in tennessee were you can look for stones in all different colors?

theres this attraction somewhere in TN were you can buy a bag in different sizes and you can fill it with as many minerals/stones/rocks as you can find and you can take them home but you dont find the stones in the water you find them on the ground and I was wondering if anyone knew the name of this place? I seen it on some tv show about vacations and attractions and they showed people in some kind of cave structure or something (but they werent underground) and they were squatting on the ground looking for stones and putting them in the bags