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How to Grow a Stalactite

Stalactites are long, slender icicle-shaped formations that hang from the roof of limestone caves. They form naturally when water seeps through the rocks in a cave's ceiling. As the water drips down, it gradually dissolves small amounts of limestone, or calcium carbonate, into formations that eventually become stalactites. You and your kids can recreate this process at home in a fairly simple science project and grow your own stalactite.

Things You'll Need

Two medium-sized jars
Warm water
Baking soda
String or yarn
Paper clips
Paper plates or cardboard
Food coloring

Instructions

- 1
  Fill two medium-sized jars about 2/3 full with warm water.
- 2
  Add baking soda and stir until it all dissolves, forming a thick paste. Start by slowly adding about 1/2 cup of baking soda. The consistency is more important than the amount of soda added.
- 3
  Place a paper plate or cardboard underneath the two jars about 8 inches apart.
- 4
  Attach a paper clip to each end of a string of yarn.
- 5
  Put an end of the yarn with the paper clip into each jar, making sure to leave a bow in the string between the jars.
- 6
  Leave the jars alone for a few days, as your stalactite begins to grow down from the string.

Rocks & Minerals