Science Insider
why are some chicken eggs are brown and some are white?
Vidunenahawula Website (National Institute of Fundamental Studies)
Ever wondered why are some chicken eggs are brown and some are white? All eggshells are made of calcium carbonate and the white ones have no pigment added. The brown colour is from a pigment that is laid down on the egg called protoporphyrin IX (PPIX), which is like the haem group in haemoglobin in your blood.It is coated on the outside of the egg as it moves through the oviduct.
