THE JUDICIOUS SELECTION AND PRESERVATION OF TUFF AND TRAVERTINE BUILDING STONE IN ANCIENT ROME*

The Republican and early Imperial monuments of Rome are, for the most part, built of tuffs quarried from at least seven pyroclastic deposits erupted from nearby Monti Sabatini and Alban Hills volcanoes. Remarks by Vitruvius (2.7.1–5), field observations of the monuments, and petrographic and rock testing studies of samples from Roman quarries demonstrate that Roman builders developed a good knowledge of the diverse material properties of the tuffs over centuries of use and exposure. Measurements of compressive strength, specific gravity, water absorption and adsorption of water vapour confirm that the petrographic characteristics of each tuff lithology strongly influence its strength and durability. Early construction utilized weakly durable, soft or vitric tuffs such as Tufo del Palatino or Tufo Giallo della Via Tiberina that are susceptible to decay, as at Temple C (290 bc ) of the Largo Argentina Sacred Area. Late Republican structures, such as the Temple of Portunus (80–90 bc ), employed somewhat durable, vitric–lithic Tufo Lionato reinforced with travertine, a durable limestone quarried near Tivoli. Roman builders selected the material properties of the tuffs to advantage for specific structural elements within large public monuments of the first century bc and the first century ad , as at the tabernae of the Forum of Caesar (46 bc ), where an upper storey of lightweight Tufo Lionato is supported by robust, lithic–crystal Lapis Gabinus pillars and flat arches reinforced with travertine. The tuffs are not very durable building stones; Romans preserved them with protective stucco, and travertine and marble cladding. Their high water intake, coupled with direct exposure to rain, daily fluctuations in relative humidity and urban weathering at present makes them especially vulnerable to decay.     

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.     

APPLICATIONS OF PETROGRAPHY AND ELECTRON MICROPROBE ANALYSIS TO THE STUDY OF INDIAN STONE SCULPTURE*

Examples of research on ancient Indian stone artefacts utilizing petrographic examination coupled with qualitative and quantitative electron beam microprobe analysis of specific minerals are described. Types of artefacts discussed include Gandharan schist sculptures. Pala dynasty phyllite and schist objects from eastern India, Hoysala sculptures from Karnataka state (southern India), and sandstone objects from northern India. In spite of the rich history of stone sculpture in the Indian subcontinent, characterization studies to date have been limited in scope, typically involving unprovenanced artefacts. The examples described point to areas in which more extensive research could produce useful information for the provenancing of artefacts.     

SHAFT‐HOLE AXES FROM CAPUT ADRIAE: MINERALOGICAL AND CHEMICAL CONSTRAINTS ABOUT THE PROVENANCE OF SERPENTINITIC ARTEFACTS*

The change of raw materials used to produce stone axes during the Neolithic to Copper Age transition in northeastern Italy, central and western Slovenia and northwestern Croatia (Caput Adriae) has been recently linked to the development of early European metallurgy. Serpentinite shaft‐hole axes occur commonly in the archaeological context of this region and their rounded irregular shape suggests that the raw material was mainly sourced from secondary deposits. The aim of the present study is to characterize with multiple analytical methods, including synchrotron radiation, the axes and locate the primary outcrop(s) of raw materials and related secondary exploitation areas. All the analysed artefacts are manufactured from peridotites and probably pyroxenites completely metamorphosed in greenschist facies and characterized by antigorite, diopside and magnetite, sometimes rimmed by penninite. Mineralogical and petrographic data exclude most Eastern Alps outcrops as possible raw material sources, thus limiting the research to the Hohe Tauern. Chemical data reveal a close homogeneity for the peridotite‐derived axes and therefore demonstrate a selection of the most suitable raw material for axe production. Provenance from Hohe Tauern and related secondary deposits of the Drava River hydrographical system agrees with previous studies, as this region is rich in copper ore deposits, which have been exploited since prehistory.     

SAND FOR ROMAN GLASS PRODUCTION: AN EXPERIMENTAL AND PHILOLOGICAL STUDY ON SOURCE OF SUPPLY*

This paper reports the results of an experimental study performed on Campanian littoral sand, together with a careful philological analysis of Pliny's text concerning the production of glass using the above sand in order to verify its suitability. Accurate chemical and mineralogical characterization of sand samples and experimental glasses was carried out, proving the unsuitability of sand for glass production in its original state. Taking into account both the results of the philological analysis of Pliny's text and the mineralogical assemblage of the sand, a new hypothesis regarding Roman glass‐making technology is proposed and tested here. The technology implies the production of ‘quartz‐enriched’ sand by means of selective grindings according to the different degrees of hardness and cleavage of the mineralogical phases. Melting experiments, carried out on treated sand and in the temperature range compatible with Roman technology, yielded a glass with composition similar to those of typical Roman glasses. Therefore, new perspectives on the sources of supply of raw materials, hitherto debated, are opened up.     

THE IMPACT OF SOLUBLE SALTS ON THE DETERIORATION OF PHARAONIC AND COPTIC WALL PAINTINGS AT AL QURNA,EGYPT: MINERALOGY AND CHEMISTRY*

The wall paintings of Al Qurna in Egypt were studied by means of XRD and ICP–AES in order to determine their mineralogical and chemical composition, and to evaluate the impact of soluble salts on their deterioration, including the identification of the building materials and pigments used. Soluble salts analysis showed that NaCl is the most common soluble salt in the bedrock, ground water and surface water samples. The building materials are affected by the ground water, while the wall paintings in the area are affected by the Upper Egypt climatic conditions, which were studied in order to detect their role in the deterioration cycle in the area.     

CHARACTERIZATION OF PLASTERS AND MORTARS AS A TOOL IN ARCHAEOLOGICAL STUDIES: THE CASE OF LARDIRAGO CASTLE IN PAVIA,NORTHERN ITALY*

Plasters and mortars from Lardirago Castle (Pavia, northern Italy) have been characterized by means of petrographical and chemical analyses in order to achieve technical and historical evidence of material production. The study focused on the oldest nucleus of the structure, where hidden plastered masonry has been discovered recently. Textural and compositional data of the binder and the aggregate fractions were collected by means of optical microscopy and electron microscopy coupled with microanalysis. These data permit the identification of building materials with similar technical and compositional characteristics, which can be related to different building phases.     

ESTIMATION OF THE BULK COMPOSITION OF FINE-GRAINED MEDIA FROM MICROCHEMICAL AND BACKSCATTER-IMAGE ANALYSIS: APPLICATION TO BISCUIT WASTERS FROM THE BOW FACTORY SITE,LONDON*

Microprobe and digitized electron-backscatter image data reveal that eighteenth-century Bow porcelain consists of a silica polymorph(s) (25–43 vol. %), a calcium phosphate phase (42–55%) with homogeneous and stippled textural variants, and a silicon-, aluminium-, and calcium-rich, former melt phase represented by discrete domains (14–20%) and micron-scale blebs that occupy 20–70% of the stippled calcium phosphate. Bulk compositions calculated from these data are deficient in calcium phosphate components and more siliceous than those determined by microprobe analysis of fused powders of the same samples. This reflects difficulties in determining representative values for the composition and volume of the melt phase, and underscores the limitations of the method where applied to media containing compositionally- or texturally-heterogeneous phases.     

ON THE WHITE AND COLOURED MARBLES OF THE ROMAN TOWN OF CUICUL (DJEMILA,ALGERIA)

This paper reports the results of an archaeometric study of the local and imported marbles found in the Roman town of Cuicul (now Djemila, Algeria), a research project funded by the Sixth Framework Programme of the European Union. Of the few imported coloured lithotypes that have been found, four are of Greek origin and one was imported from Asia Minor. In addition, two other classical Roman coloured stones found on the site are probably of local North African origin (most likely one from Numidia and one from Algeria). With regard to the grey and white marbles employed in the statuary and architecture, petrographic study in thin section and the δ¹³C and δ¹⁸O isotopic data emphasize the frequent use of the local fine‐grained lithotype from Filfila (Skikda) together with imported Greek lithotypes (i.e., Pentelic marble, the dolomitic variety of Thasian marble, and Parian marble from Lakkoi) as well as different varieties of the so‐called ‘greco scritto’, whose provenance in some cases still remains uncertain. In fact, the petrographic and geochemical features of the marbles do not always match those known for the classical ‘greco scritto’ from the quarry of Cap de Garde, near Annaba (Algeria).     

ON THE AGE AND CONTENT OF JAR‐35—A SEALED AND INTACT STORAGE JAR FOUND ON THE SOUTHERN PLATEAU OF QUMRAN*

An intact and sealed storage jar known as Jar‐35 was found in 2004, south of the Qumran settlement. A previous study identified tartrate in the deposit of the jar, indicating the possible past presence of wine ( Buti et al. 2006 ). However, we cannot confirm this finding. Using liquid and gas chromatography with mass spectrometric detection, no trace of tartaric acid or salts thereof could be detected in our samples. We show that the major component of the deposit is gypsum. No other organic compounds were identified with the methods that we have applied. Both radiocarbon dating of charcoal in the deposit and thermoluminescence dating of the ceramic jar show that it dates to the main period of habitation at Qumran (c. 100 bc to ad 70).     

THE CHEMICAL COMPOSITION OF BLUE PIGMENT ON CHINESE BLUE‐AND‐WHITE PORCELAIN OF THE YUAN AND MING DYNASTIES (ad 1271–1644)*

The chemical compositions of the glazes and pigments of 39 blue‐and‐white porcelains of Ming Dynasty date and three of Yuan date were examined by SR‐XRF. Both the analysis of the Fe/Mn ratio in the light blue areas of the glaze and a comparison of the Fe/Mn values between light blue, dark blue and clear glaze areas reveals that the samples can be divided into three groups. The results indicate that there are two significant changes of provenance of blue pigment during the Ming Dynasty and that some kinds of pigment were most probably imported from the Middle East. Considering literature records and other scholars’ studies, an outline picture of the pigment used on Chinese blue‐and‐white porcelain produced in Jingdezhen in the Yuan and Ming Dynasties is presented.