Stalactites form from the deposition of calcium carbonate, a natural substance found in limestone. When mineral-rich water drips from cave ceilings, it leaves behind tiny amounts of calcium carbonate as it evaporates. Over time, these deposits accumulate, creating the icicle-like formations known as stalactites. Similarly, stalagmites form on cave floors from the droplets that land there, often a result of the same process. Stalactites are typically found in limestone caves, where the specific conditions allow for such mineral-rich water to flow and create these unique geological structures.