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How do stalactites and stalagmites form from dissolved calcium compounds?

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A labeled diagram of the periodic table entry for calcium, showing its atomic number 20, symbol Ca, atomic weight 40.078, electron configuration, and classification as an alkaline-earth metal. Icons indicate calcium is a solid with a face-centered cubic crystal structure and strongly basic oxides at room temperature. — calcium The chemical element calcium is the most abundant metallic element in the human body.

Stalactites and stalagmites are speleothems formed primarily from calcite, a form of calcium carbonate dissolved from limestone bedrock.123

The process begins when rainwater absorbs carbon dioxide from soil, creating a dilute carbonic acid. As this acidic water percolates through limestone, it dissolves the calcium carbonate and carries it downward through rock fractures.3

When the water emerges from the ceiling of a cavern, it encounters the cave atmosphere. The release of carbon dioxide from the water reduces its ability to hold the dissolved mineral in solution, causing the calcium carbonate to precipitate.23

Stalactites: Form as water hangs from the ceiling, depositing a ring of calcite around the edge of each drop. Over time, these rings build downward into a hollow, icicle-like tube.13
Stalagmites: Form on the cave floor where the mineral-rich water droplets land. As the water hits the floor, further precipitation occurs, building up layers of calcite into mound-like or columnar shapes.13