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Quaternary International, 2016
The Equotip Hardness Tester is applied to different types of quartz and other lithic raw materials in order to determine if variations in the rebound hardness measured by this device may serve as a proxy for detecting the levels of continuity and isotropy of toolstones. Continuity, the amount of cracks and other internal defects; and isotropy, the measure of the directional properties of a raw material, are known to have important effects on the level of consistency and predictability of fractures, which in turn is traditionally considered a main factor for defining the flaking quality of a given raw material. The results demonstrate the existence of differences among the raw materials analysed in both the average value and the variability of the rebound hardness. While cryptocrystalline samples show the most homogeneous results, quartz and metamorphic rocks display a comparatively higher variance. In the specific case of quartz, such variability seems to be mainly caused by the presence of internal planes and discontinuities, while anisotropy, although also active, had played a comparatively modest role. The results achieved by the Equotip Hardness Tester suggest that this device could be successfully used for a basic or preliminary estimating of some of the physical and mechanical properties of stone raw materials. Therefore, it is a potential index test for complementing other, more accurate, laboratory methods.
For the study of chert to be of use to archaeologists, researchers must adopt a standardised method of analysing, describing and cataloguing geological chert types and chert artefacts. It is the primary purpose of this article to propose a standardised system of analysis of chert in archaeology. In the proposed system, characteristics are of two categories - macroscopic and microscopic. Macroscopic analysis describe the following categories of characteristics: appearance, colour, pattern and cortex. Within each of these categories is a set of characteristics, each with specific means of measurement and terminology for recording measurements. There are five categories of microscopic characteristics to describe when viewing thin sections – structure, texture, matrix, grains and grain composition. It is hoped that such a system will be adopted and applied to both artefacts as well as geological samples of known provenience. By adopting a standardised methodology and terminology for the macroscopic and microscopic analysis of chert, archaeologists can improve the efficiency, the ease and the dissemination of their research.
Conservar Património, 2020
Chert tools from Galería and Gran Dolina Caves, located in the Sierra de Atapuerca site complex (Burgos, Spain), were characterized (macro-visual inspection, mineralogical phases, degree of crystallinity, soluble salts, surface morphology and optical surface roughness) and compared to chert samples collected from the surrounding Atapuerca mountain range. The chert tools were studied to determine their causes of decay and for selecting the most compatible consolidation treatments. It was found that samples solely containing quartz were not significantly altered and required little conservation treatment compared to those that contained quartz and moganite, which were more weathered and powdery, requiring consolidation. The efficacy of the consolidating products traditionally used by conservators (acrylic resin and ethyl silicate) to preserve these chert remains, together with novel nanoparticle-based products (SiO2 and a mixture of SiO2 and Ca(OH)2 nanoparticles) were assessed in thi...
Archaeological and Anthropological Sciences, 2018
This paper contributes to an understanding of the distances and choices involved in raw material procurement strategies by Upper Palaeolithic communities through a Pyrenean geoarchaeological case study. Methodologically it involved using Particle Induced X-ray Emission (PIXE) with a focused proton beam to determine the concentration and distribution of elements in geological samples from three natural primary outcrops belonging to two geological formations outcropping in the French side of the Pyrenees. While it was not possible to distinguish the formation through reference to major and minor elements, some variations were revealed at the trace elemental level. With the aim to determine if these elements were associated with the Si matrix or to a specific inclusion, elemental maps were acquired and the elemental composition of the identified inclusions were also determined. These chemical signatures were then compared to those generated from archaeological artefacts from sites in northern Spain as a means of reconstructing the catchment areas used by prehistoric groups for their chert procurement. The results indicate the existence of trans-Pyrenean long distance procurement strategies during the Magdalenian (13700 to the 18800 cal BP).
Raw material mechanical tests were conducted to answer the question whether differences in raw material procurement among Early Upper Palaeolithic populations in Moravia (Czech Republic) may have been driven by different mechanical properties of those materials. Characterization of mechanical properties of erratic flints and Krumlovský les I type chert show that the relatively finer-grained erratic flints, preferred by local Aurignacian populations, are more easily and probably also predictably knapped at higher speeds, such as reached with soft (antler, wood) percussors, whereas cherts of Krumlovský les I type, exploited by both Szeletian and Aurignacian populations, are more resistant to fracture propagation. This implies the suitability of the former material for fine blade and bladelet production, and of the latter to projectile (e.g. Szeletian leaf points) manufacture, and possibly explains the export of leaf points from Szeletian areas (the Krumlov Forest) to Bohunician and Aurignacian sites within Moravia. Exploitation of erratic flints was easier as regards Aurignacian, and probably entire Upper Palaeolithic knapping technology. Certain tasks, however, were better met with other raw materials, thus reflecting the rela-tivity of chipped stone raw material quality perception in the Palaeolithic.
Archaeological and Anthropological Sciences, 2017
Understanding details of stone tool procurement and transfers is for a major research avenue in improving our knowledge about prehistoric societies. The accuracy of the provisioning sources identifications is based on the establishment of large regional repositories. Recent studies show that specific investigations on the evolution of cherts were effective in distinguishing primary sources from the various secondary sources of a raw material. In this paper, we focus on another difficulty that is the distinction between different primary sources of the same geological layers. We consider the specific case of the Bedoulian cherts from southeastern France. This chert was exploited and circulated over large distances during the whole prehistoric record. It is particularly known to have been heat-treated during Late Chassey culture (Neolithic). We show in this paper that paleogeographical variability exists due to variations in the bioclastic and detrital components. With the support of foraminifera data, the granulometry of detrital quartz grain provides the possibility to distinguish between different primary sources. A first test in archeological contexts illustrates the efficiency of the method as well as indicates major changes in provisioning practices between upper Paleolithic and Neolithic groups.
Recent exploratory studies have suggested the potential of magnetic susceptibility (MS) as a rapid and low-cost sourcing technique for lithic archaeological materials. Most commercially available susceptibility instruments, however, do not have the sensitivity to characterize weakly susceptible cherts and silicified woods. Comparative results from nine chert, two silicified wood, a porcellanite, and four obsidian sources using a highly sensitive, calibrated, and magnetically-shielded instrument allow exploration of MS variability within and between geological sources. Color, texture, grain size, and large inclusions of cherts and obsidians are not straightforward determinants of MS. Weathering rinds (patinas) and cortex from a variety of cherts yield reduced MS values, as does a recrystalized cobble of Rio Maior flint, indicating that magnetic mineral removal during chemical weathering and diagenesis is more prevalent than staining or other mineral penetration of cobbles. In situations of multiple overlapping MS ranges, analysis is limited to discriminating cherts with high or low MS range distributions, for example in an atypicality index. Some silicified woods, obsidians, and porcellanites possess a much greater range of intersource variability, and thus sourcing analysis is more likely to be broadly successful using the susceptibility of these materials. Unexpected results from an archaeological test using a historic lithic assemblage from Azinheira, Portugal, indicate that assemblage MS may be influenced by practices of raw material selection. Understanding variability in lithic MS has relevance for the design of most source geochemical sampling, as well as the behavioral interpretations that result from such investigations. ᭧