An investigation into the architecture and composition of a urinary calculus.

A bladder stone of diameter of 16 mm was sectioned to reveal an internal structure showing some complexity. Visually apparent were concentric rings divided into two principal zones. The outer zone comprised large single interlocking crystals, but the inner zones consisted of a much more fragile environment in which large single crystals were embedded in a much finer matrix. More detailed analysis was performed on the stone's layers using X-ray diffraction which is capable of identifying the crystallites but may also be used to elucidate some of the crystallite characteristics and thereby provide evidence for the growth environment. Proton induced X-ray emission was carried out at a number of points along a radius of the sample to examine the distribution of key trace elements. A possible mechanism for the influence of this banding on the fragility of the stone is discussed.