Stalactites are not necessarily speleothems (i.e limestone concretions in caves) but can also be pagothems or ice stalactites, as in this photo. A pagothem is therefore a spike of ice in the shape of a generally straight and pointed cone which forms when water drops or trickles down a surface towards a corner and freezes in the cold. In windy conditions, or if the water falls very slowly, the stalactite may curve slightly.