ROCK PHYSICS AND THE NEOLITHIC AXE TRADE IN GREAT BRITAIN*

This paper is concerned with the products of a number of Neolithic quarries in highland Britain. It investigates the claim that the scale of axe distribution was partly the result of social factors which resulted in these artefacts gaining an added value in areas remote from their sources. One case study considers the sequence of production in Cumbria, in relation to the tensile strength of the rock quarried in different parts of the region. It shows that these considerations had only a limited influence over the choice of stone source and the scale on which it was worked. A second study compares the tensile strength of the main raw materials used for making non-flint axes with the extent to which these sources were actually exploited. Again there is only a limited relationship between the two, suggesting that social factors may indeed have been important.     

MECHANICAL PERFORMANCE OF QUARTZ-TEMPERED CERAMICS: PART I,STRENGTH AND TOUGHNESS*

The effect of quartz temper on the physical and mechanical properties of clay ceramics and the elucidation of the underlying mechanisms that are responsible for these effects are presented here. Characteristics studied included bulk density, open and closed porosity, density of impervious portion and fracture morphology. Mechanical behaviour was studied by measuring energy dissipation during fracture, Young's modulus, initial fracture toughness and strength in flexure. The significant increase in toughness with quartz volume fraction is explained by the development of a model that accounts for the crack distribution around the grains. The archaeological implications of the work are discussed on the basis of all the parameters that might affect the potter's choices of raw materials.     

METALLURGY OF BRONZE USED IN TOOLS FROM MACHU PICCHU,PERU*

Although the tin‐bronze artisans’ tools found at Machu Picchu appear to have been cast to their final shape, examination of their microstructures shows that they were forged and annealed. As found, the tools were broken or cracked due to poor ductility of the bronze. Rolling and annealing of samples of bronze formulated with sulphur and iron additions to replicate the metal used at Machu Picchu show that the minimum amount of deformation needed to induce the observed recrystallization is a 12% reduction in thickness. The sulphur and iron impurities retard nucleation of new grains during annealing, but do not inhibit subsequent grain growth. Tensile tests show that while up to 10% porosity in cast bronze has no effect on hardness or initial strain‐hardening rate, it reduces the tensile strength and ductility enough to embrittle the metal. Hardness is an inadequate indicator of the strength properties of cast bronze intended for use in tools or weapons. The results show that when the metalsmiths at Machu Picchu started making bronze tools for use by stone and woodworkers, they had not mastered the art of making metal with adequate strength properties for this service. The forging and annealing procedure they used did not enhance the mechanical properties of their tools, and may reflect an inherited metallurgical tradition.     

MORTAR STUDIES TOWARDS THE REPLICATION OF ROMAN CONCRETE

The use of strong and durable materials is one essential ingredient leading to the survival of many monumental Roman concrete structures. Replicated concrete mortars with different lime to pozzolan ratios, encompassing the range likely to have been used by the Romans, have been studied here to determine their relative compressive strengths as a function of time. This has been supplemented by the use of the scanning electron microscope to delve into the structure and composition of the binders formed within the strongest and weakest mortars, leading to a deeper understanding of the reasons for the differences in compressive strength.     

A NOVEL APPROACH TO STUDIES OF PREHISTORIC EXPLOITATION OF STONE TOOL MATERIALS USING MATERIAL COMPOSITION,SURFACE MORPHOLOGY,MICROSTRUCTURE AND MECHANICAL PROPERTIES*

For a comprehensive understanding of material exploitation in prehistory, we applied advanced analytical methods to Japanese prehistoric stone tool materials. Compositions, surface morphologies, microstructures and mechanical properties of the primary lithic materials were analysed. As a result of the tests on actual Palaeolithic artefacts, preferential material selection was observed based on composition, structure and other physical properties of the materials. Homogeneous materials composed of a single type of mineral—α‐quartz—were intentionally selected for Palaeolithic tools regardless of the type of rock. These materials unexceptionally present higher hardness and strength. Moreover, materials composed of extremely fine crystal grains of ~0.1 µm in size with highest hardness and strength were selectively used for sharp‐edged blades. These results lead us to the conclusion that quantitative and objective analyses will give us precise information on prehistoric materials, which will enable us to make an analytical approach to the comprehension of prehistoric exploitation of stone materials. This could eventually complement the traditional interpretation of material exploitation based on conventional petrological classifications.     

THE RELATIONSHIP BETWEEN LITHOLOGY,FLAKING PROPERTIES AND ARTEFACT MANUFACTURE FOR AUSTRALIAN SILCRETES*

Mechanical properties of Australian silcrete strongly influenced raw material selection and artefact manufacture. Microcrystalline silcrete, with high compressive and tensile strength, is suitable for blade tools requiring fine retouch. Fine‐grained silcrete (high compressive strength but lower tensile strength) was often used for blade‐based implements, but is more susceptible to edge fracturing. Medium‐grained silcrete has poor flaking properties (low compressive and tensile strength) and was often used for flake manufacture. Thus material determinism can explain much of the variability in silcrete artefact morphology and assemblage composition. Silcrete compressive strength is positively correlated with percentage of microcrystalline matrix and negatively correlated with average grain size, so hand lens examination of a silcrete sample can give a good indication of its likely flaking quality.     

MECHANICAL PERFORMANCE OF QUARTZ-TEMPERED CERAMICS: PART II,HERTZIAN STRENGTH,WEAR RESISTANCE AND APPLICATIONS TO ANCIENT CERAMICS*

Mechanical performance of ceramics can be measured by various techniques. Conventional testing usually requires multiple samples of large size and specific geometries and for this reason cannot be usually applied directly to ancient pottery. However, Hertzian strength and wear resistance can be measured on the same specimen, of small size, and it is shown that these tests can describe, to a good approximation, the basic ceramic mechanical propertics (strength and toughness). Therefore, these tests are proposed for use on archaeological specimens. An application on Punic amphorae found in Corinth is presented.