An investigation of microscopic calcareous spherulites from herbivore dungs

Microscopic spherulites have been reported from a number of archaeological sites, frequently associated with fresh or burnt animal dungs. Theories to explain their presence have centred around the views that they represent (a) plant-derived calcium oxalate that has passed through the animal gut, or (b) an unspecified calcium salt produced by the animal itself. This paper presents data to show that the spherulites are minute (typically 5-15 mu m) spheres of radially crystallized calcium carbonate surrounded by an organic coating. They can be found in the dung of a range of herbivores grazing on calcareous pastures. On limited current evidence they appear to be commonest in sheep, intermediate in cow, and absent from rabbit. A clear distinction exists between these spherulites and the larger, more coarsely crystalline calcium oxalate druses found in most herbaceous and arboreal plant matter. (C) 1997 Academic Press Limited.