An introduction to uSe wear

Key to beginning observations and describing observations of use-wear is to remember that wear mechanisms are not mutually exclusive. They are not the result of a single, independent event. Rather use-wear mechanisms interact during tool use and processing and one type of use-wear becomes more dominant depending on the contact surfaces and materials between the surfaces (Adams 2014:30–31). The observable use-wear is likely the result of the most recent use of the tool, although there could be a cumulative effect based on the main use (Adams 2010:47; Hamon 2014:119; Revedin et al. 2015:83). Macroscopic and microscopic analysis for this research included an evaluation of the overall asperity and topography of working surface, surface modifications of the stone’s grains including distribution over the surface, and presence or absence of tribological wear including adhesions, abrasions, fractures and sheen caused by tribochemical reactions (Dubreuil 2004:1615; Hamon 2014:119). The wear types described in more detail on the linked web pages been adopted by archaeologists and tribologists (Adams 2014:30–36; Adams et al. 2009:47; Bhushan 2013; Blau 2012:5–2, 5–9; Singer 2012:2–2; Stachowiak and Batchelor 2014:577–584, 594).

Even before analyzing the use surfaces of artifacts, a study of the experimental and ethnographic collection with known use and wear patterns was completed to become familiar with the types of patterns that can form (Adams 2014:72–73; Dubreuil 2001:77; Dubreuil and Savage 2014:140; Hayes 2015; Keeley 1974:326). Consideration was also given as to other forms of wear that can manifest and not be related to use, such as depositional, excavation, and storage wear.

Figure 1. Brizaf mathan Coarse smooth comparison

Figure 2. Ethnographic Brizaf3&2 Mațhan – area sampled from smooth textured section (circled in Figure 1) In this smooth section the asperities are becoming rounded, there is overall levelling, and the crystals are becoming less distinct (71X)

Figure 3. Ethnographic Brizaf3&2 Mațhan – area sampled from coarse textured section (rectangle in Figure 1) Topographic differences are indicated by protruding asperities (examples shown with arrows) and defined crystal borders(69X)

Figure 4. SN 0319 Ona Adi Madit B1:9:21 Middle Aksumite, natural light Using only natural light the asperity tip fractures become apparent (irregularly shaped reflected light) (65X)

1 / 4

There are various options for observing and describing use-wear: macroscopic analysis of topography; microtopography to describe the degree of irregularity of the surface; low microscopy to distinguish nature of contact surfaces; and high magnification to see the impact of wear on individual grains and to determine mineral inclusions. High powered magnification to observe wear on individual grains can be achieved with silicon or acetate peels that can fit under or into a high-resolution microscope (Adams et al. 2009:47–48, 54; Dubreuil and Nadel 2015:3; Fullagar et al. 2017:178; Hayes 2015:124, 182–189; Longo 2018 pers. comm.). High powered microscopes were unavailable, and although originally the plan was to apply peels to artifacts and return them to Canada for analysis under high powered microscopes, I was unable to complete the final data collection scheduled for spring 2020 because of Covid-19 pandemic travel restrictions. For this project macroscopic and a low powered digital microscope (Dinolite^tm) were used to analyze grinding stones and offered a very good opportunity to observe the surface wear.

Important lessons were learned during this analysis. As well as other published methods, it is important to consider the kinetics at use on these large grinding stones. Taking a microscopic image from one area could be very different than from a different area of the surface. Pressure is applied differently along the surface, some areas are not experiencing any or little friction to cause tribological reactions (Figures 1 - 3), and resurfacing (hammering) occurs often, often eradicating previous use-wear. Additionally, the type of lighting can affect how wear is seen under the microscope (Figure 4).