Newberyite in ancient and modern urinary calculi: identification and space group.

Relatively large amounts of newberyite, MgHPO(4).3H(2)O, are found in old or very large urinary calculi. Single crystals of struvite, MgNH(4) PO(4)6H(2)O, sometimes show some decomposition to newberyite on aging. The fact that large amounts of struvite are also found in ancient stones implies, however, that special conditions, as yet unknown, are required for decay to occur.