Asked by Claire Brevick
Stalactites form by deposition of various minerals held within a water solution that slowly drips vertically from the ceiling of an underground cavern or structure. As the water droplets hang, they deposit contained
minerals (often calcium carbonate). Continued downward growth in this manner is how a stalactite forms (or the reverse for stalagmites). The simplest stalactite form is a thin, hollow straw, but if excess water ﬁlters through or around the central body, then bulbous, tapered mineral cones can develop too.