Analysis of vaterite microspherolith deposits on a pure cholesterol gallstone by X-ray diffraction, X-ray microanalysis and infrared absorption techniques.

Minute globular concretions of light-green and light-brown colour were found as deposits in the pits at the rough surface of a pure cholesterol gallstone. They were analyzed by scanning electron microscopic, X-ray diffraction, X-ray microanalytical and infrared absorption spectrometric methods. In scanning electron microscopy, the concretions appeared as ovoid microspheroliths varying from 5 to 30 micron in size. The microspheroliths presented smooth and rough surfaces; the reason for these different types of surface remained unclear. X-ray diffraction and infrared absorption analysis revealed that the microspheroliths were mainly composed of vaterite and the host plate-like crystals were cholesterol. By energy-dispersive X-ray microanalysis, large quantities of calcium without significant quantities of phosphorus were detected in the microspheroliths. Calcium was absent in the plate-like crystals and could not be detected in the central part of the stone. In the pigmented periphery of the stone, some silicon and iron were found. The presence of calcite, aragonite and iron-containing pigment materials in the concretion is suggested. From the textural point of view, the analytical data strongly suggest that the stone-forming conditions suddenly changed from a cholesterol-favourable stasis condition to a condition favoring the deposition of calcium carbonate possible as the result of haemorrhage.