Differences between Stalactite and Stalagmite

Stalactite vs. Stalagmite

Stalactites and stalagmites are types of speleothems, or cave formations, that are created by the deposition of minerals. The primary mineral involved in these formations is calcite, a form of calcium carbonate. They form when rainwater seeps through cracks in limestone, dissolving the calcite. As this water drips into a cave, it deposits the minerals, which build up over long periods to create these distinct structures. When a stalactite and a stalagmite grow together, they form a column.

Comparison Table

Category	Stalactite	Stalagmite
Location	Hangs from the ceiling of a cave.	Rises from the floor of a cave.
Growth Direction	Grows downwards.	Grows upwards.
Shape	Typically icicle-shaped, long, and thin with a pointed tip. It can start as a hollow tube called a "soda straw".	Generally has a broader base and a more rounded or flattened top. It is solid and does not begin as a hollow structure.
Formation Process	Formed by mineral-rich water dripping from the cave ceiling. The minerals are deposited before the water droplet falls.	Formed from the mineral deposits left by water droplets that fall to the cave floor.
Etymology	From the Greek word stalaktos, meaning "dripping".	From the Greek word stalagmias, meaning "the result of dripping".
Mnemonic Device	"Stalactites hold on tight to the ceiling," or contain the letter 'c' for 'ceiling'.	"Stalagmites might reach the ceiling," or contain the letter 'g' for 'ground'.

Venn diagram comparing Differences between Stalactite and Stalagmite

Composition and Types

While the most common stalactites and stalagmites are speleothems found in limestone caves, these formations can be composed of other materials as well. Besides calcite, they can contain other minerals such as other carbonates, opal, chalcedony, and limonite. The color of these formations can be influenced by their mineral content, with pure calcite being white or colorless, and impurities like iron adding shades of red, orange, or black.

Formations similar to stalactites and stalagmites can also occur in environments other than caves. These include lava tubes, where molten lava can create "lava stalactites" or "lavacicles". Ice stalactites, commonly known as icicles, form when water drips and freezes. Additionally, these structures can form on man-made concrete structures due to the leaching of calcium ions.