Stalagmites are similar in appearance and physics to stalactites, but instead of facing downwards from the ceiling, they face upwards from the ground. These can usually be found in the caves under Middle-Earth, and can be collected with any type of pickaxe.
However, be warned! Stepping on stalagmites will cause damage, and falling onto one causes even more damage, so be careful in caves!
Because of their ability to deal damage, they can be very useful for mob farming and grinding, or simply just trolling your friends!