As the redeposited minerals build up after countless water drops, a stalactite is formed. If the water that drops to the floor of the cave still has some dissolved calcite in it, it can deposit more dissolved calcite there, forming a stalagmite.

What happens if you touch a stalagmite?

Stalagmites should normally not be touched, since the rock buildup is formed by minerals precipitating out of the water solution onto the existing surface; skin oils can alter the surface tension where the mineral water clings or flows, thus affecting the growth of the formation.

How do stalagmites get their shape?

Water drips from stalactites hanging from cave ceilings. Each successive drop adds a thin layer of minerals to a growing stalagmite below. ... Simulations of their growth tend to assume that water droplets fall straight down, resulting in candlestick shapes.