Water, upon seeping inside the rocks, dissolves small amounts of calcium carbonate present in the rocks. When this water drips from cracks or small openings in the ceiling of the cave, it evaporates because of warm air within the cave and also due to the air currents present. While the water evaporates, a tiny amount of calcium carbonate that it had dissolved gets deposited to form a speleothem. Thus, speleothems are formed by accumulation of calcium carbonate by water droplets.