The Cramp of the Dead
A Neolithic tomb chamber and two Bronze Age cists, part of a cairn structure, were discovered in Crantit Farm, Mainland Orkney, and excavated by GUARD during the summers of 1998 and 1999. The western cist contained: a) cremated bone, b) vitrified fuel ash slag (VFA), known as cramp in the context of Bronze Age Orcadian funerary practices, and c) plant remains said to be the material used for the basket that carried the cremated bones from the funerary pyre to the final resting place i.e. the cist.
Crantit Cist cramp is a composite material produced by the reaction of fine silica-rich soils in the presence of bone, at high temperatures (not exceeding 700-9000C) with the aid of fluxes provided from fuel ashes.
Cramp formation is part of the events taking place at the tail end of the process of cremation after the organic components of the body, funerary furniture and other combustible materials had burned off, and the cremated bone fractured in small fragments and reached ground level.
The reaction may involve the breakdown of calcium phosphate to calcium oxide and phosphorus pentoxide (vapour). Calcium oxide is indeed seen reprecipitated as calcium carbonate on the stone floor of the cist and on the basket fragments, as well as fine crystallites within the pores of the cramp. Phosphorus pentoxide may, under reducing conditions be trapped by the cramp glass.
It is clear that by both its chemistry and mineralogy and by the fact that it was buried in the cist next to the cremated bone, that the “cramp of the (Crantit) dead” was viewed not as mere pyre debris but as an integral part of the deceased – perhaps ultimately the deceased’s final “fusion” with “mother earth” from which he/she “derived”.
Click here to read our Oxford Journal of Archaeology article
|SEM-BS image of the interface zone between glass and bone showing the formation of bone “drops” (bar= 200 microns; x 120).||
Demonstration of reprecipitation of hydroxylapatite (bone) dissolved in carbonic acid (low pH soil water). As CO2 degasses, hydroxylapatite becomes increasingly less soluble until it precipitates. It precipitates before calcite. Hence, calcite is unlikely to precipitate from a solution of acidic groundwater containing dissolved bone assuming CO2 loss is the reason, as is usual, for calcite precipitation. Computed using The Geochemist’s Workbench (Bethke 1996).