Science project

Limestone Formation

The goal of this experiment is to explore the formation of limestone as it happens in nature. Calcium carbonate is the main component that forms shells, and when marine life dies those shells settle on the bottom of the ocean where they collect. Over time, limestone is formed.


How is limestone formed?


  • Pieces of shell
  • Shoebox
  • Plastic garbage bags
  • Paper cups
  • Dry plaster
  • Water


  1. Line the shoebox with a plastic bag and cut it to fit snugly.
  2. Pour plaster and water into the bag/box and mix thoroughly.
  3. Add the shell pieces to the plaster mixture.
  4. Pour the mixture into paper cups.
  5. Place the cups in a warm place and leave them undisturbed.
  6. After 5 days, remove the limestone mixture from the cups.
  7. Compare the homemade limestone to natural samples.

[NOTE: For a more complex project, vary the locations of the paper cups and note the difference between samples.]

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