The composition of calculi from patients with alcaptonuria.

SUMMARY The composition of the crystalline material present in 5 renal calculi and pieces of prostatic calculi from patients suffering from alcaptonuria has been determined by the X-ray powder method. The urinary stones contain standard calculus constituents. Some of the pieces of the prostatic calculi consist of a substituted calcite Ca(Mg, Mn)CO3, a substance not reported hitherto in a calculus. The stones, which are very dark in colour, also contain a small amount of the crystalline melanin-type oxidation product of homogentisic acid and probably a larger amount of the pigment in a finely divided or amorphous state.