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The Witch's Finger in the Carlsbad Caverns

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.

The Hall of Giants in the Carlsbad Caverns

The corresponding formation on the ceiling of a cave is known as a stalactite. If these formations grow together, meeting in the middle, the result is known as a column.

There are various mnemonics to help remember which formation hangs from the ceiling (stalactite) and which rises from the floor (stalagmite):

• StalaCtite has a "c" for "ceiling".
• StalaGmite has a "g" for "ground".
• The T in StalacTite resembles one hanging from the ceiling, while the M in StalagMite resembles a formation rising from the floor.

• Stalactite is stretched "tite" (tight) by hanging from the ceiling.
• Stalactites hang on tight to the ceiling, Stalagmites might get there.
• Stalagmite pushes up with all its "mite" (might) from the floor.

• "When the mites go up, the "tites" (tights) come down".
• Stalactites sag down like an old woman's t**s

When touring caves with stalactites and stalagmites you might be requested to not touch the rock formations. This is generally because the formation is considered to still be growing and forming. Since the rock buildup is formed by minerals solidifying out of the water solution onto the old surface, skin oils can disturb where the mineral water will cling, thus affecting the rock formation.

Stalagmites can also form in lava tubes, although the mechanism of formation is much different. Stalactites and stalagmites can also form on concrete ceilings and floors, although they form much more rapidly there than in the natural cave environment.

• Stalactite
• Bashful elephant
• The Witch's Finger
• Mercer Caverns

• The Virtual Cave: Stalagmites
• Cave of the Mounds