Abstract

Slices of cortical bone taken from femur mid-shaft selected from lead-coffined burials at Spitalfields (a XVIIIth Century crypt) were X-rayed on to non-screen film using standard clinical techniques. Anomalous degrees of opacity were observed from some of the X-ray images. Chemical analyses of the bone samples showed concentrations of Pb up to 37 weight percent, and Sn up to 3.16 weight percent. In areas of extreme replacement, the lead phosphate mineral pyromorphite (a member of the apatite group) was identified. Other metals displaying unusually high concentrations include Fe, Cu, Zn, Ag, Sb and Cd. Electron microprobe analysis, coupled with backscattered electron imaging, showed the Pb and Sn distributions in some of the samples to be of a heterogeneous (but systematic) nature, with the highest concentrations of these elements occurring in the outermost regions of the bone. Localised enrichments of these elements were also observed around osteon canals throughout the cortex. X-ray diffraction studies of orientated sections of cortical bone showed a correlation between the concentration of Pb and changes in the diffraction profile between 31 degrees and 33 degrees 2Theta (using Cu K a radiation) towards Pb-rich hydroxylapatite. The concentrations of Pb and Sn recorded here are, of course, far in excess of any possible life-time levels, and illustrate the extent of extreme post-mortem alteration and recrystallisation of bone, in the presence of solutions rich in these elements, over a period of less than 200 years. However, the bone still retains many of its histological characteristics.

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