Each drop leaves calcite crystals on the cave ceiling or walls or floor. The crystals adhere to each other and grow into different kinds of formations. Eventually, stalactites reach down from the ceiling, stalagmites tower upward from the floor and sheets of flowstone cover the walls. Speleothems grow slowly. The rate of growth depends on how fast the water flows and on how much dissolved calcium carbonate it contains.
Stalactites are speleothems which form on the ceiling of a cave.
All stalactites begin as hollow circles when crystals of calcite form around the outer surface of a droplet of water hanging form the ceiling. As each new drop of water appears, it leaves another crystal ring. Soon long crystal soda straws hand from the ceiling. These tubular stalactites grow into cones of icicles if the initial tube becomes plugged and the crystals from around its outer surface. Sometimes water trickles along the cave's ceiling and walls leaving thin trails of crystals.