MECHANICAL PROPERTIES OF STONE ARTEFACT MATERIALS AND THE EFFECT OF HEAT TREATMENT*

Mechanical testing of lithologies used for stone tool manufacture has shown that fracture toughness is the most objective measure of the quality of raw materials shaped by either flaking or pecking/grinding. Materials amenable to pressure flaking and blade manufacture have low values of fracture toughness, whereas those shaped by pecking/grinding have high values. The fracture toughness test is also the most definitive for quantifying the improvement in flaking properties of materials subjected to intentional heat treatment. Cryptocrystalline and macrocrystalline siliceous lithologies demonstrate a well-defined, gradual reduction in fracture toughness with increased temperature. When heated to optimum temperatures, their fracture toughness approaches that of obsidian, the lithology generally regarded as having the best flaking properties.     

AN ASSESSMENT OF COMPOSITIONAL AND MORPHOLOGICAL CHANGES IN MODEL ARCHAEOLOGICAL GLASSES IN AN ACID BURIAL MATRIX

The degradation mechanisms of glass in a buried context result in surfaces that have been depleted in various elements. The stability of the glass is primarily affected by the burial environment and the glass composition. However, in all archaeological glasses, the corroded layer that is formed on the surface tends to be low in alkalis, high in silica and lacking in cohesion. The extent to which the material has degraded, along with the physical nature of the corrosion, has a profound effect upon a wide range of factors affecting the stability of artefacts, as well as the choice of conservation techniques to be employed. This study has a number of objectives: determination of the morphology of the surface of the leached layer in glasses of two different compositions with different surface finishes; examination of the transition between the corroded material and the unaffected substrate; and investigation of concentration profile of different elements within the surface layers, as a function of depth. The study uses two glasses, fabricated under laboratory conditions, to replicate two common glass types found in the historical environment; a soda–lime–silica glass typical of those found in the Roman period throughout the Mediterranean and northwestern Europe, and high‐lime–potash glasses typical of those of Western Europe in the late medieval period. Three different surfaces have been prepared to mimic alternative manufacturing techniques such as blown, cast and ground surfaces for each composition. The glasses have been corroded under controlled laboratory conditions to replicate the buried environment. Imaging and chemical information is obtained using SEM–EDX and morphological information using IFM to produce 3‐D mapping from topographical surfaces.     

ROMAN AND MEDIEVAL GLASS FROM THE ITALIAN AREA: BULK CHARACTERIZATION AND RELATIONSHIPS WITH PRODUCTION TECHNOLOGIES*

Compositional investigations were performed on 81 Roman and medieval glass fragments (first to 14th centuries ad ) from four Italian archaeological sites. The samples were soda–lime–silica in composition, with natron as flux for the Roman and early medieval glass samples, and with plant ash as flux for the late medieval ones. The varying colours are due to the differing FeO, Fe ₂ O ₃ , MnO and Sb ₂ O ₃ contents. Hierarchical cluster analysis identified six compositional groups related to age, which were compared with those found in the literature. In this way, technological continuity from the Roman to the early medieval period and the appearance of plant ash technology in the ninth century, 200 years in advance of the period previously believed, are demonstrated.     

Ancient agriculture and domestic activities: a contextual approach studying silica phytoliths and other microfossils in soils

Abstract

Based on microfossil and soil data, we discuss a different methodological approach to agricultural and domestic archaeological studies, taking two Formative sites in the north-west Argentinian high valleys (province of Catamarca) as case studies, independently of traditional datasets and historical analogies. As a result of our investigations we not only recognised the vegetal species cultivated in ancient fields (dated to c. AD 800) but also distinguished some of the agricultural practices, such as crop rotation and alternation, use of animal fertilisers and irrigation resources, as well as the abandonment of the site. From this perspective, corral episodes could also be distinguished. In residential enclosures, we obtained results concerning activity areas, the definition of floors and the identification of reoccupations.     

Fuel Fodder and Faeces: An Ethnographic and Botanical Study of Dung Fuel Use in Central Anatolia

Abstract

The Norse inhabited Greenland between AD 1000 and AD 1500 and, toward the end of the occupation, according to archaeological evidence, they were predominately marine mammal hunters. Despite the fact that marine resources became important for subsistence, the Norse Greenlanders settled the area in o?der to farm. This is indicated by site locations, faunal material, archaeobotanical, and palynological evidence.

Phytolith analysis from a quern stone, likely made from stone of local origin, found at Gården Under Sandet, a Norse farmstead in Greenland, was examined to determine if there was any evidence indicating domestic cereal processing. The phytoliths found on the quern stone can be associated with grasses and sedges, but the absence of dendritic phytoliths likely indicates that the quern stone was not used to grind seed. This preliminary study demonstrates that information about Norse agriculture may be obtained by examining the phytolith remains from a quern stone.