Stalactite-Stalagmite Column - A coral limestone cap covers much of Barbados. Surface rainwater filtering downwards through the coral to underground streams and aquifers, becomes saturated with calcium carbonate, the main component of limestone. Stalactites are the calcium carbonate deposits left behind by water dripping from the roof of caves and cliff overhangs. Stalagmites, on the other hand, are the corresponding calcium formations that grow upward from the ground.