Eggshells are made up of almost entirely calcium carbonate, which is also found in our bones, teeth, and nails. They also contain protein, magnesium, selenium, and strontium, which are said to be good for bones and joints. Eggshell powder can be used as a calcium-intensifying agent in food and confectionaries. Eggshells can be used as a natural repellent to deter snails, slugs, and other garden pests. Eggshells contain calcium carbonate, which is used as an abrasive in some toothpastes to help remove stains. Eggshells can be added to compost to improve the quality of the compost and enrich the soil with nutrients. Eggshell powder can be used as a calcium feed additive to promote the growth of poultry and livestock.