Time for some egg facts! Ever wonder what makes your egg shell so brittle, or why you get an especially bright yolk sometimes? Egg shells are made from calcium carbonate, a substance that occurs naturally in many forms–for instance, limestone and chalk are both members of the same family! Beta carotene, a pigment found in many plants and fruits–like carrots!–is sometimes added to feed to provide that extra bit of yellow in the yolk.
Source: Miranda JM, Anton X, Redondo-Valbuena C, et al. Egg and egg-derived foods: effects on human health and use as functional foods. Nutrients. 2015;7(1):706–729. Published 2015 Jan 20. doi:10.3390/nu7010706.