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Stalactites and Stalagmites

Seattle, WA
stalactites, stalagmites, caves, geology, earth, minerals, crystals, calcite, stone, rocks
Stalactites and stalagmites in Bridal Cave, Missouri

Stalactites and stalagmites are the icicle-like mineral formations found in caves around the world. Stalactites (remember: T for top) hang from the top of caves whereas stalagmites (remember: G for ground) rise from the ground. They are formed from rainwater carrying mineral deposits that drip into the cave. When the water drops interact with the cave air, they leave behind their minerals which compound over an extremely long period of time and eventually form stalagmites and stalactites.

stalactites, stalagmites, caves, geology, earth, minerals, crystals, calcite, stone, rocks
Stalactites in Rawhiti Cave, New Zealand

Most stalactites come in a cone-shaped structure, thick at the base and end at a narrow point, but some are hollow and extremely fragile straw-like structures called helictites. Most stalactites are made up of calcite and aragonite crystals.


Stalagmites often form under stalactites from the remaining water droplets that fall to the ground, but both structures aren’t interdependent. Stalagmites tend to grow outwards, so they are mostly cone shaped or flat and are thicker than stalactites.

stalactites, stalagmites, caves, geology, earth, minerals, crystals, calcite, stone, rocks
Stalagmites in a cave at the Apuseni Mountains, Romania

The average growth rate of stalactites and stalagmites is less than 10 cm every 1000 years, some are over 190,000 years old! Temperature and rainfall also factor into the time it takes for them to form.


Stalactites and stalagmites come in multiple colors depending on the mineral that they are made up of. Many times a variety of minerals make up a stalactite or stalagmite, resulting in nature’s wondrous cave decorations.


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