Abstract

To better understand the variously proposed origins of pisoliths, it is useful to compare cave pearls and pisoliths with respect to their properties, mechanisms of growth, and depositional environments. Cave pearl formation is restricted to the cave environment. Cave pearls occur in a shallow-pool setting, often behind rimstone dams or terraces, where carbonate material accretes layer by layer over a clastic nucleus. Slight agitation or dripping slowly turns the pearl so that radial layers form evenly and concentrically around the nucleus. Irregular pearl shapes may be caused by overcrowding, insufficient agitation and rotation, and subaerial exposure where the pool level descends below the tops of the pearls. Polygonal packing, inverse graded bedding, directional elongation, and “microstalactitic” textures – all reported features of pisolite – may also occur within cave pearl settings.