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Characterization of Color and Composition in Chert for Grouping and Comparison
María de Uribe-Zorita1, Pedro Álvarez-Lloret1, Silvia Bottura2 and Celia Marcos1*
1Department of Geology, University of Oviedo, Oviedo, Spain
2HERCULES Laboratory, Évora, Portugal
Submission:June 23, 2023; Published: July 05, 2023
*Corresponding author:Celia Marcos, Department of Geology, University of Oviedo, C/ Jesús Arias de Velasco s/n 33005, Oviedo, Asturias, Spain
How to cite this article: María de U-Z, Pedro Á-L, Silvia B, Celia M.Characterization of Color and Composition in Chert for Grouping and Comparison. Glob J Arch & Anthropol. 2023; 13(2): 555858. DOI: 10.19080/GJAA.2023.13.555858
Abstract
Color is one of the most commonly used characteristics in archaeological studies to differentiate and describe chert. In this study color parameters of a collection of cherts from different outcrops have been quantified using reflectance’s measured in the range of 300-800 nm with a spectrophotometer; in addition, the color cluster analysis and the correlation between color and chemical composition were analyzed with SPSS program
Keywords:Chert; Color; Reflectances; CIELab; SPSS
Introduction
Chert is a rock of siliceous composition whose major phase is micro to cryptocrystalline silica in addition to other phases present (micas, carbonates, iron oxides, etc.) as well as organic matter that gives flints dark tones [1]. Chert is one of the most important materials used as a resource by Stone Age humans, and color is one of the most used characteristics in archaeological studies to differentiate and describe chert. Chert shows a great variability of color and texture along the same geological formation, as pointed out by Frederick Ringstaff [2]. This property is difficult to determine, as it depends on many factors, as the perception of the person observing it, the external light source providing the illumination, the composition, structure and texture of the chert. The objective of this study was to quantify color parameters and to analyze the correlation of color with chemical composition. The final purpose is to have color references of chert from different geographic and geological origins for use in archaeological tool characterization studies.
Methodology
The analyzed cherts belong to outcrops from different geographical locations, mainly European (Spain and France) and American (USA and Venezuela) (Figure 1). The composition of the elements expressed in oxides (%) has been obtained by X-ray fluorescence with a Shimadzu EDX-720 equipment. The chromatic coordinates were obtained from the chert reflectances measured with an Edinburgh Instrument FS5 spectrophotometer in the range of 300- 800 nm, at 5 nm intervals. The CIE 1931 diagram [3] was used to represent the chromatic coordinates. RGB code and CCT (K) color temperature were obtained using the NIX converter [4]. The color cluster analysis and the correlation between color and composition were calculated with the SPSS statistical program (IBM SPSS Version 24).
Results
The results obtained from the quantification of the color parameters and the oxide composition of the flint samples are presented in Table 1. The Pearson correlation between the CCT(K) and the oxide composition of the studied cherts (Table 2) is, in general, very low, except for Fe2O3 (-0.8), TiO2 (-0.6) and SiO2 (0.7). In the CCT (K) dendrogram (Figure 2) 3 groups have been established, concordant with the groups established in the CIE 1931 chart (Figure 3a) and Figure 3b. Black flint samples have not been considered because they are outside the CIE chart.
L (Location): 1 Sants-Montjüic, Barcelona; 2 Pontils, Tarragona; 3 Área Metropolitana y Corredor de Henares, Madrid; 4 Sisante, Cuenca; 5 Sant Pere de Riudebitlles, Barcelona; 6 Lorca, Murcia; 7 Rubí, Barcelona; 8 L’Hospitalet de Llobregat, Barcelona; 9 Gràcia, Barcelona; 10 Les Borges Blanques, Lleida; 11 Dordogne, Francia; 12 Libourne, Francia; 13Arangas, Asturias; 14 Asiego, Asturias; 15 Ballota, Asturias; 16 Arizona, EEUU; 17 Northern Guarico-Lake Valencia Area, Venezuela; 18 Venezuela; 19 Montana, EEUU; 20 Texas, EEUU; 21 Sotres, Asturias; 22 Vidiago, Asturias.
Conclusion
The color of the studied chert presents few variations among them since their chromatic coordinates are very close due to the fact that the elemental composition is similar in all of them. This color behavior in the chert studied so far seems to be a trend for others, regardless of their provenance and origin. It is likely that more pronounced differences between the chert can be obtained from reflectances measured in infrared regions, work that is planned to be carried out in the near future.
Acknowledgement
Spanish Ministry of Science and Innovation (No. PID2020- 112832RB-I00). Spanish State Plan for R+D (No. HAR2017- 82557-P). Smithsonian museum.
References
- Luedtke BE (1992) An Archaeologist's Guide to Chert and Flint. Archaeological Research Tools 7. Institute of Archaeology, University of California, Los Angeles, California.
- Frederick CD, Ringstaff C (1994) Lithic resources at Fort Hood: Further investigations. In: Trierweiler WN (Ed.), Archaeological Investigations on 571 Prehistoric Sites at Fort Hood, Bell and Coryell Counties, Texas. Mariah Associates Inc.: Austin, Texas, USA.
- CIE 1931 http://sciapps.sci-sim.com/CIE1931.html
- nixsensor.com/free-color-converter/
