Opal uroliths from a ram

Abstract

The exanimation of uroliths from a ram under the petrological microscope, and by chemical and physical techniques, revealed that the greater part of the uroliths consisted of opaline silica. Most of the opal was authigenic, being derived from the soluble silica ingested by the grazing animal in its plant feed. Possible mechanisms for the precipitation of authigenic opal are discussed. Some of the opal was present in the form of' particles which were identified as phytoliths, silicisponge spicules, and frustules of diatoms. The presence of these allothigenic particles in uroliths raises complex pathological issues which are discussed briefly.