CONVERTING CATHODOLUMINESCENCE SPECTRAL DATA INTO CHROMATICITY DIAGRAMS FOR PROVENANCE ANALYSIS OF QUARTZ GRAINS

The link between the cathodoluminescence (CL) color of quartz grains and provenance is well established. However, studies on this association are constrained by each individual's visual perception. To eliminate this subjective factor, we used CL spectral data to generate a chromaticity diagram to investigate the origin of quartz grains from an archeological site in the Negev Desert. We relied on the chromaticity diagram adopted by the International Commission on Illumination (CIE) named CIE 1976 L*u* v* color space, commonly known as CIELUV (Robertson, 1977). This diagram lacks luminance components that are equivalent to light intensity. It means, for example, that dark or light green have the same position in the plot, thus providing color matching and reproduction without considering attributes like saturation or hue. Notably, the CIELUV display approximates how the human gamut senses colors by rendering them through visually appealing luminosity perceived as neon colors. The numerical data plotted in the CIELUV is derived by converting spectral data into a system of coordinates named u’ and v’. These coordinates are calculated using data from a spectral count at each wavelength weighted by a factor of color-matching functions (e.g., Ford and Roberts, 1998). This graphical representation is advantageous because it eliminates the subjective factor when analyzing color by providing a cartesian coordinate system for color mapping and descriptive statistical data analysis. Using the chromaticity diagram associated with spectral energy-emission components, we segregated sediments from different sources in the archeological site.

References

Ford, A., Roberts, A., 1998. Colour Space Conversions. Westminster University, London.

Robertson, A.R., 1977. The CIE 1976 Color-Difference Formulae. Color Research & Application 2, 7–11.