How big is a stack?
Each item type has a different stack size, with consumable items usually between 30 and 999.
Stone has a stack size of 999, as do many of the similar basic resources such as dirt and sand.
It depends on the item, weapons can only stack on one, the only weapons that can stack are Light Disks and Banarangs. Potions can only stack up to 30 when Explosives stack up to 99. Most blocks stack up to 999.