The word speleothem comes from the Greek words spelaion meaning "cave" and thema meaning "deposit".
The most well-known speleothems are stalactites and stalagmites.
Stalactites grow down from the cave ceiling.
Stalagmites grow up from the cave floor.
It’s easy to remember which is which:
Stalactites have a "T" for top and stalagmites have a "G" for ground.
Caves, stalactites and stalagmites are caused by chemical reactions.