Crystallization of calcite from amorphous calcium carbonate: earthworms show the way

Darwin (1881) was one of the first scientists to formally record that earthworms excrete calcium carbonate granules, with some up to 2 mm in diameter. However, since Darwin’s studies they have received relatively little attention. The function of the granules remains a mystery, but may be related to regulation of Ca, CO 2 , pH or some other as yet undiscovered metabolic process (Robertson, 1936; Piearce, 1972). There has recently been an increase in research activity focussed on earthworm calcium carbonate granules driven by the work of Canti (Canti, 1998, 2007; Cantian d Piearce, 2003) and largely relating to their potential use in archaeology.