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A first attempt to quantify use-related polish on quartzite by using Laser Scanning Confocal Microscopy
Adrian Evans  1@  , Antonella Pedergnana  2, *@  , Andreu Ollé  3, 4@  
1 : School of Life Sciences, University of Bradford  -  Site web
England, West Yorkshire, BD7 1DP, UK. -  Royaume-Uni
2 : Institut Català de Paleoecologia Humana i Evolució Social  (IPHES)  -  Site web
​Zona Educacional 4, Campus Sescelades URV (Edifici W3) 43007 Tarragona -  Espagne
3 : Institut Català de Paleoecologia Humana i Evolució Social  (IPHES)  -  Site web
Zona educacional 4 (Edif. W3), Campus Sescelades URV, 43007 Tarragona, Spain. -  Espagne
4 : Àrea de Prehistòria, Universitat Rovira i Virgili, Fac. de Lletres  (URV)  -  Site web
Av. Catalunya 35, 43002 Tarragona, Spain. -  Espagne
* : Auteur correspondant

Several methods have been applied in the past to attempt to quantify use-wear on stone tools (e.g. digital image acquisition, atomic force microscopy, laser profilometry, focus variation microscopy, laser confocal microscopy). Despite this, quantification studies are still in their infancy and none of them have been systematically incorporated into the domain of traceology, due to the paucity of standardised methods (see Evans et al., 2014).

More efforts to develop this branch of study are needed, as the possibility of quantifying wear features, which are currently subjectively described, would allow to take a significant step forward in the development of the discipline. In fact, one of the most controversial aspects of traceology itself, very frequently emphasized by non-supporters of the method, is the preclusion of providing numerical quantifications of the surface modifications photographed by use-wear analysists.

While several attempts have been made to quantify wear on chert (or flint), only one case study is currently found in the literature involving quartzite and it focused on the use of scale-sensitive fractal analysis on a very limited range of contact materials (Stemp et al., 2013).

In order to fill this methodological gap, we performed a first trial to quantify polished surface on quartzite through Laser Scanning Confocal Microscopy (LSCM). The main objective was to understand if metrological analysis could be a viable option to ascribe the analysed polish to specific worked materials. If so, the interpretation of the worked material from the analysis of polished surfaces would be based on objective data and would acquire a more significant meaning.

Experiments focused on the performing of the same action (i.e., unidirectional scraping) on 5 materials (wood, bone, antler, fresh hide, dry skin, and cane) all conducted with flakes coming from the same quartzite cobble. Confocal Microscopy was used to obtain quantitative data of polished surfaces formed after the contact with the different materials. This data is mathematically described using standardised ISO aerial surface parameters, such as roughness and waviness, and are then statistically analysed to evaluate the ability for such measures to distinguish polishes. In this contribution, we present preliminary measurements of polished areas on quartzite, and we discuss the potential of the LSCM in the identification of the worked material.

A secondary, but not less important, objective was to compare the images taken with Scanning Electron Microscopes and LSCM of the same polished areas to better appreciate the visual characters of the polished areas. In fact, we noticed that both the optical and laser images of the LSCM are incredibly explicative of the micro-topography of the analysed surfaces.

Evans, A.A., Lerner, H., Macdonald, D.A., Stemp, W.J., Anderson, P.C., 2014. Standardization, calibration and innovation: a special issue on lithic microwear method. Journal of Archaeological Science, 48: 1-4.

Stemp, W.J., Lerner, H.J., Kristant, E.H., 2013. Quantifying microwear on experimental Mistassini quartzite scrapers: preliminary results of exploratory research using LSCM and scale-sensitive fractal analysis. Scanning, 35: 28-39.

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