Composition of bladder stones in Rwanda.

A small area of endemic bladder stone formation occurs in Rwanda, Central Africa. The X-ray diffraction of 13 of these stones revealed that they were mainly composed of calcium oxalate monohydrate. By X-ray fluorescence the presence of considerable amounts of rubidium was demonstrated which was measured by atomic absorption spectrometry. The concentration of rubidium was about 2-5 times greater than that of zinc. Thy hypothesis that rubidium is an important lithogenic element is formulated. It might explain this endemic bladder stone formation which is exceptional for Central Africa.