Science Experiment: Grow-Your-Own Speleothem Replicas

Grow-Your-Own Speleothem Replicas

Cave formations like stalactites and stalagmites, collectively known as speleothems, form as water seeps through limestone. As the water moves through the rock, it dissolves small amounts of limestone also called calcium carbonate. When the water drips from a cave ceiling, small amounts of the mineral calcite (also called calcium carbonate) are left behind, eventually leaving an icicle shaped stalactite; water droplets that fall to the cave floor deposit calcite to form stalagmites. Following the instructions below will allow you to simulate and observe how speleothems form in a cave using water and the mineral salt.

You will need: water, thick-natural fiber string (cotton butchers twine works well), cardboard, 2 jars, Epsom salts

  1. Fill each jar with water. Add enough Epsom salts in each jar of water to form a thick solution.
  2. Place the jars on the piece of cardboard about six inches apart. Soak the string in the solution until it is completely saturated.
  3. Place one end of the string in one jar of solution. Place the other end of the string in the other jar of solution. Leave enough slack so there is a bow in the string, but do not let the string touch the cardboard.
  4. Leave the jars and the string in an accessible and observable location for several days while a salt “stalactite” and “Stalagmite” begin to form. CAUTION: Once these salt “speleothems” begins to form, any movement of the string could cause them to break.

Cave Connection!

As the water moves into the cave, it dissolves small amounts of limestone also called calcium carbonate. When the water drips from a cave ceiling, small amounts of the mineral calcite (also called calcium carbonate) are left behind, eventually leaving an icicle shaped stalactite; water droplets that fall to the cave floor deposit calcite to form stalagmites.