Stalactite / Stalagmite

The difference between stalactite and stalagmite are mites go up tites come down. Stalactite hang from the "C" ceiling and stalagmite "G" grow from the ground.

Here is a little experiment that someone has done. It show how stalactites are formed.
Nice little reference.

A stalactite (Greek stalaktites, (Σταλακτίτης), from the word for "drip" and meaning "that which drips") is a type of speleothem (secondary mineral) that hangs from the ceiling or wall of limestone caves. It is sometimes referred to as dripstone.

Stalactites are formed by the deposition of calcium carbonate and other minerals, which is precipitated from mineralized water solutions. Limestone is calcium carbonate rock which is dissolved by water that contains carbon dioxide forming a calcium hydrogencarbonate solution.

A stalagmite (from the Greek stalagma ("Σταλαγμίτης"), "drop" or "drip") is a type of speleothem that rises from the floor of a limestone cave due to the dripping of mineralized solutions and the deposition of calcium carbonate.

Lavacicles are geological formations resembling small round-tipped stalactites that are found in lava tubes, the name comes from their resemblance to icicles.

Lavacicle is really a generic term that encompasses several different types of stalactites found in lava tubes.