Published online by Cambridge University Press: 15 February 2011
Avian eggshells are one of the most rapidly calcifying systems known. Although the entire shell contains ∼ 97 weight % CaCO3, etching in EDTA reveals great spatial variability in etching rate. A correlation between the etching rate of various regions and the relative positions of the different parts in the calcium reserve assembly (CRA) has been made; the CRA is the source of calcium during natural decalcification by chick embryos.