Mineralogical notes of apatite in urinary calculi

Apatite in some samples of common urinary calculi consisting mainly of apatite or of calcium oxalate and apatite was subjected to X-ray and thermal analysis and electron microscopic investigation. The X-ray analysis has determined the lattice parameters agreeing with hydroxyapatite, and the mean crystallite size normal to the basal plane in a range of 200-800 A. The thermal analysis is given by differential thermal analysis (DTA) and thermogravimetric (TG) curves. From the TG curve of a mixed apatite-calcium oxalate calculus, an approach is given to estimate the proportions of the constituent materials; the result is as follows: whewellite, 51.7%; weddellite, 16.6%; apatite, 19.1%; and organic materials, 12.6%. Analysis with the scanning electron microscope with energy dispersive X-ray spectrometer has shown that apatite is found as tiny spherules (5-10 micrometer in diameter) with fluffy surfaces resulting from projecting fine fibers or needles (about 0.5 micrometers in length). The fibers are considered to be mosaic aggregates of crystallites. The spherules fill interspaces of well-formed oxalate crystals or are included sporadically in individual crystals. Occasionally well-formed crystal-shaped oxalates are bordered with narrow bands consisting of apatite spherules (often as hemispheres) linked in a row.