Spherical to elliptical peloids, averaging 80 mu m in length, occur inside plant rootlets that penetrate limestones of the Pleistocene Ironshore Formation on Grand Cayman. The peloids, which are associated with desiccated fragments of mites, are formed of minute calcite platelets and fragments of algal and/or fungal filaments bound by organic-rich material. The calcite platelets are morphologically similar to platelets that occur in the epidermal cells of the surrounding rootlets. The peloids probably originated as fecal pellets produced by mites which mined into the softer cores of the roots. In so doing, they recombined the calcite platelets, algal/fungal filaments, and organic material into coprogeneous material. Subsequent diagenetic modification produced peloids formed of micrite that are morphologically identical to peloids found in many caliche units.