Concise Oxford Dictionary of Archaeology (801 page)

Destructive method for determining the mineralogy of crystalline materials such as ceramic, glass, stone, and corrosion products derived from certain kinds of metal. The sample is powdered and mounted either on a glass slide or on a platform to fit within an X-ray camera. Monochromatic X-rays are focused on the sample and the transmitted rays are then recorded using X-ray plates or photographic film. The spacing between crystal lattice planes in different mineral species and the incident angle of the X-ray beam determine the series of X-ray intensities that are transmitted through the sample and onto the recorder. The identification of minerals is based on the spacing between high-spots in the diffraction pattern while relative concentrations can be estimated using the intensity of signal recorded. Sample matching can be done manually or statistically to group similar materials and to relate such groups to potential source materials.

 
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Non-destructive method for determining the elemental composition of natural and man-made materials such as ceramic, glaze, glass, obsidian, pigments, paint, and coins as an aid to determining their source, technology of production, and similarity to other examples of comparable style or form. A sample is exposed to an X-ray source causing it to fluoresce and emit secondary X-rays. The wavelengths of the released energy, known as fluorescent X-rays, are detected and measured as a spectrograph. Component elements can be identified on the basis of the unique wavelength of their fluorescent X-rays, while concentrations can be estimated from the intensity of the released X-rays. Since only the surface of an object is studied, care needs to be taken that corrosion and decay do not affect the analysis.

 
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See
SCANNING ELECTRON MICROSCOPY
.

 
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Specialized form of
X-RAY FLUORESCENCE SPECTROMETRY
involving the use of an instrument that allows a small and highly focused X-ray beam to be directed at a pre-selected point on the surface of a sample. Secondary X-rays emitted from the target point are directed to a detector and analysed as a spectrograph to reveal the presence and relative concentration of different elements. The great advantage of the technique is its ability to examine very small areas such as individual layers of paint or single minerals within a sample; there is, however, the associated danger that materials are characterized on the basis of unrepresentative samples.

 
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Manner of depicting humans and animals on rock art panels in which the skeleton and internal organs form part of the motif. Especially characteristic of rock art in northern Australia where most of it appears to have been produced over the last 3000 years, although some may be as old as 6000 bc.

 
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See
X-RAY FLUORESCENCE SPECTROMETRY
.

 
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