What Makes Up Egg Shells?

Egg shells come in many colors and sizes, but they all consist of the same major components. The egg shell's function is to protect the developing bird embryo inside and to provide it with the calcium it needs to grow.

Calcium Carbonate

About 95 percent of an egg shell is calcium carbonate, which has a chemical formula of CaCO3. Calcium carbonate, a crystal structure, provides a strong bond, while allowing space for other substances to exist, or for air and moisture to pass through the shell.

Other Substances

Egg shells also contain calcium phosphate, magnesium carbonate, sodium, potassium, zinc, manganese, iron, copper and proteins. Such substances help make the egg shell stronger.

Fun Fact

Although egg shells look solid, they contain an average of 9,000 pores and can contain up to 17,000 pores. As eggs age, carbon dioxide leaves the egg, which is what makes boiled, older eggs easier to peel than fresh eggs.

References

• Exploratorium: Anatomy of an Egg
• University of Florida IFAS Extension: Concepts of Eggshell Quality
• Chemical and Engineering News: Chicken Eggs