THE SCIENTIFIC IDENTIFICATION OF ARCHAEOLOGICAL JET-LIKE ARTEFACTS

Jet has been widely used in the past for jewellery but was just one of a range of black lithic materials employed. When worked into small objects these materials can be visually indistinguishable, yet discrimination is important because of the restricted occurrence of jet. X-ray fluorescence (XRF) is a rapid non-destructive discriminatory technique, but not all samples are clearly classified, and inhomogeneity may pose problems. A reassessment of the use of XRF is reported. Other techniques considered include electron spin resonance, infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy and X-radiography. These were tested on geological materials to define an effective methodology for archaeological material. The recommended approach is a combination of XRF and X-radiography, although preliminary Fourier transform infrared results showed promise. The X-ray techniques were tested on Romano-British assemblages from Catterick and Stanwick.     

THE PROVENANCE AND COAL RANK OF JET BY CARBON-13 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY

The carbon-13 nuclear magnetic resonance spectra of jet samples from England and Spain resemble those of carbonaceous materials from lignitic and sub-bituminous ranks. This characterization is based on the aromatic/aliphatic ratio of resonances and on the pattern of fine structure. Particularly characteristic of jet is the well-defined fine structure in the aromatic region that may be attributed to phenolic functionalities. This fine structure is found in all English and Spanish samples. Resonances from rapidly moving methyl groups are found in English but not in Spanish samples and may provide a means of distinguishing provenance.     

COAL AND CREMATION AT THE TSCHUDI BURN,CHAN CHAN,NORTHERN PERU*

Analyses of a 20–30 cm thick, completely combusted ash at the 25 × 70 m Tschudi burn at Chan Chan, northern Perú, contain 52–55 wt% SiO₂, 180–210 ppm zirconium and are consistent with coal ash. Soil geochemistry across the burn showed elevated calcium and phosphorus content, possible evidence for reported human cremation. A calcined, 5 g, 4.5 cm skull fragment recovered from the burn was confirmed as human by protein radioimmunoassay (pRIA). X‐ray diffraction showed that the bone had been heated to 520°C. The burn took place c. ad 1312–1438 based on interpretation of a ¹⁴C date on carbonized plant tinder.