RADIOGRAPHICALLY OPAQUE BONES FROM LEAD-LINED COFFINS AT CHRIST-CHURCH, SPITALFIELDS, LONDON - AN EXTREME EXAMPLE OF BONE DIAGENESIS

Slices of cortical bone taken from femur mid-shaft selected from lead- coffined burials at Spitalfields (a XVIIIth Century crypt) were X-raye d on to non-screen film using standard clinical techniques. Anomalous degrees of opacity were observed from some of the X-ray images. Chemic al analyses of the bone samples showed concentrations of Pb up to 37 w eight percent, and Sn up to 3.16 weight percent. In areas of extreme r eplacement, the lead phosphate mineral pyromorphite (a member of the a patite group) was identified. Other metals displaying unusually high c oncentrations include Fe, Cu, Zn, Ag, Sb and Cd. Electron microprobe a nalysis, coupled with backscattered electron imaging, showed the Pb an d Sn distributions in some of the samples to be of a heterogeneous (bu t systematic) nature, with the highest concentrations of these element s occurring in the outermost regions of the bone. Localised enrichment s of these elements were also observed around osteon canals throughout the cortex. X-ray diffraction studies of orientated sections of corti cal bone showed a correlation between the concentration of Ph and chan ges in the diffraction profile between 31 degrees and 33 degrees 2 The ta (using Cu K-a radiation) towards Pb-rich]lydroxylapatite. The conce ntrations of Pb and Sn recorded here are, of course, far in excess of any possible life-time levels, and illustrate the extent of extreme po st-mortem alteration and recrystallisation of bone, in the presence of solutions rich in these elements, over a period of less than 200 year s. However, the bone still retains many of its histological characteri stics.