Journal of Archaeological Science (1999) 26, 923–933 Article No. jasc.1999.0401, available online at http://www.idealibrary.com on The Organic Geochemistry of Jet: Pyrolysis-gas Chromatography/Mass Spectrometry (Py-GCMS) Applied to Identifying Jet and Similar Black Lithic Materials—Preliminary Results S. Watts* and A. M. Pollard Department of Archaeological Sciences, University of Bradford, Bradford, U.K. G. A. Wolff Environmental Organic Chemistry and Geochemistry Group, Oceanography Laboratories, Department of Earth Sciences, University of Liverpool, Liverpool, U.K. Jet, cannel coal, lignite and torbanite are some of the materials that were used in the past to make black shiny ornaments. Distinguishing between these different materials has proven difficult. They all originate from organic sedimentary deposits, which can be classified according to the organic matter from which they were formed, the type of deposit, and its geological maturity. Pyrolysis-gas chromatography/mass spectrometry (py-GCMS) is a commonly used method for the analysis of complex macromolecules, such as the preserved organic matter found in organic-rich sediments. Preliminary results of py-GCMS analyses of samples of jet and other workable black lithic materials are reported here. Distinctive pyrolysis products were identified for each sample analysed, that reflect their different organic precursors and depositional environment. The pyrolysis products of torbanite and cannel coal samples were dominated by a series of normal hydrocarbons. Conversely, samples derived from wood precursors, such as lignite and jet produced predominantly phenol, methylphenol and methoxyphenol. The lignite and Whitby jet samples could be discriminated by the differences in the distribution of normal hydrocarbons produced on pyrolysis. Organo-sulphur compounds, such as thiophenes, were predominant in the pyrolysis products of Kimmeridge oil shale.  1999 Academic Press Keywords: JET, CANNEL COAL, LIGNITE, TORBANITE, WHITBY, KIMMERIDGE, PYROLYSIS-GAS CHROMATOGRAPHY/MASS SPECTROMETRY. Introduction T he problem of distinguishing between jet and other black lithic materials found amongst archaeological assemblages is one which has been addressed by a number of different analytical approaches (Watts & Pollard, 1996). Jet has a limited availability, and therefore is often assumed to be a high status, valuable commodity in comparison to other more ubiquitous raw materials, such as cannel coal, oil shale and lignite. This assumption can only be assessed when the different black lithic materials are reliably identified as jet or otherwise. The materials worked originate from organic matter in sedimentary deposits, and are rich in organic carbon which makes them soft and easy to carve. Microscopic examination of pol- ished sections from the artefacts provides detailed information on the organic constituents of the materials, and the type of deposit in which they were formed, and has been successfully applied to the study of selected artefacts (Smith & Owens, 1983; Teichmu ¨ ller, 1992; Allason-Jones & Jones, 1994). However, the relatively large sample size required for organic petrology precludes its use for the routine analysis of many of the small artefacts, such as beads, which are common amongst archaeological assem- blages of black shiny ornaments. An alternative approach to the study of these materials has been to analyse their inorganic elemental composition using non-destructive techniques such as X-ray fluorescence and X-radiography (Pollard, Bussell & Baird, 1981; Hunter et al., 1993; Davis, 1993). This has enabled whole artefact assemblages to be analysed, but since the inorganic constituents of organic sediments are variable, the artefacts can only be classified into broad categories of material-type and these categories are not always reliable (Watts, 1996). This paper presents the results of preliminary research into the use of pyrolysis-gas chromatography/ mass spectrometry (py-GCMS) to distinguish between *Current address: The Conservation Centre, National Museums and Galleries on Merseyside, Whitechapel, Liverpool, U.K. 923 0305–4403/99/080923+11 $30.00/0  1999 Academic Press