THE ORIGIN,DESTRUCTION AND RESTORATION OF COLOUR IN EGYPTIAN TRAVERTINE*

Travertine was one of ancient Egypt's most popular ornamental stones. Upon prolonged exposure to sunlight, the rock's translucent brownish calcite is bleached to nearly white. Ultraviolet and gamma irradiation experiments were undertaken to investigate the source of the brownish colour and the process by which it fades. It was found that the coloration results from the activation of colour centres by natural radioactivity within the rock, and that these colour centres are deactivated by the ultraviolet component of sunlight. The results also demonstrate that the original brownish colour of sun‐bleached, travertine objects can be restored by artificial gamma irradiation.     

MULTI‐METHOD MARBLE PROVENANCE DETERMINATIONS: THE CARRARA MARBLES AS A CASE STUDY FOR THE COMBINED USE OF ISOTOPIC,ELECTRON SPIN RESONANCE AND PETROGRAPHIC DATA*

A multi‐method approach, based on petrography, stable isotope data and electron spin resonance spectroscopy for assigning the provenance of white marbles, is presented. A total of 11 experimental variables has been used, including the quantitative measurement of the sample colour and its homogeneity. On this basis we attempt to distinguish the three main quarrying basins of the Carrara district, that is, Torano, Miseglia and Colonnata. Such discrimination, extremely uncertain on the basis of the single techniques, may be performed with acceptable confidence’ using a properly selected subset of six petrographic, isotopic and spectroscopic variables. The final resubstitution and jackknifed re‐assignment rates are, respectively, 85% and 81%. Inclusion of the remaining five variables into the classification rule does not improve the results, but simply increases data overinterpretation. The practical possibility of using such an approach for more general provenancing problems is considered.     

IDENTIFICATION OF STONE BLOCKS USED FOR THE BUILDING OF THE THYSDRUS AND THAPSUS AMPHITHEATRES IN TUNISIA

In Tunisia, the largest amphitheatre (known as the Coliseum) at Thysdrus (El Djem), with some parts of the second amphitheatre, and the Thapsus amphitheatre have been built with squared stone blocks (opus quadratum). The petrographic and geotechnical analyses of the samples taken from the amphitheatre blocks show that these blocks belong to the Tyrrhenian and to the Mio‐Pliocene age. Ancient quarries have been found on the Tyrrhenian dune line between Hiboun and Al Alya, at a distance of 30 km from Thysdrus, from which the Tyrrhenian blocks have been extracted. Concerning the Mio‐Pliocene blocks, they have most likely been cut from just one ancient quarry found in the hill of Ksour Essaf. The height of almost all of the measured blocks from the Thysdrus Coliseum is equal to the Punic cubit used at Carthage (50 cm), and the height of the measured blocks from the Thapsus amphitheatre is also equal to the Punic cubit (50 cm), or very close to the Roman cubit (45 cm).     

ANCIENT EGYPTIAN LIMESTONE QUARRIES: A PETROLOGICAL SURVEY*

Ancient Egyptian limestone quarries in the Nile Valley occur in six geological formations of Palaeogene age. Samples were collected from 23 of the 48 known quarries, and analysed by thin-section petrography and X-ray fluorescence spectrometry. Results of the analyses show that the geological formations can be identified from rock texture and allochem types, and a plot of SiO₂/Al₂O₃ versus CaO/[CaO + MgO]. The application of these petrographic and geochemical parameters make it possible to determine the geographic provenance of limestone used in ancient Egyptian sculptures and monuments.     

PETROGRAPHIC AND ISOTOPIC CHARACTERIZATION OF THE MARBLE OF THE ISLAND OF TINOS (GREECE)*

Most outcrops of good‐quality crystalline marble in Mediterranean countries were exploited in Greek and Roman times. Hence, a wide variety of marble is now found in archaeological excavations. The precise determination of the provenance of a marble object is of great archaeological importance, and is now mostly obtained by coupling the petrographic study of a thin section with the analysis of the C and O stable isotopes, or by stereomicroscopy and EPR. The existing databases are considerable but still insufficient, because our knowledge about and study of ancient Mediterranean quarries remain incomplete. The contribution of this research is to add new petrographic and isotopic data on small quarries on the Greek island of Tinos that were exploited in antiquity. This marble belongs to the same geological horizon; it is quite pure, sometimes dolomitic and characterized by a low‐T, high‐P metamorphism that produced a limited recrystallization (MGS varying from 0.64 to 2.50 mm) on marine limestone protoliths. The petrographic features are quite distinctive: the fabric is strongly lineated and often stressed; and the accessory minerals are ubiquitary quartz, ore minerals, graphite and muscovite. As far as the isotopic data are concerned, δ¹³C_PDB varies from 1.1 to 2.7, and δ¹⁸O_PDB from ?1.7 to ?11.4. Both the features and the data have been compared with those of similar marbles used in antiquity, showing that their combination mirrors the fingerprint of the Tinos marble.     

‘GRANITO DEL FORO’ AND ‘GRANITO DI NICOTERA’: PETROGRAPHIC FEATURES AND ARCHAEOMETRIC PROBLEMS OWING TO SIMILAR APPEARANCE

Granitoid rocks were among the stone materials most frequently used for columns and pillars during the Roman period. When employed in Rome and the Mediterranean provinces, they were mainly quarried in Egypt, in Asia Minor and in Italy. Some of these rocks show very similar macroscopic features, so it is often very difficult to tell them apart with the naked eye. This is the case with the ‘Granito del Foro’ (or Marmor Claudianum), from the Gebel Fatireh, in the Eastern Desert, and the ‘Granito di Nicotera’ (Calabria), both exploited from the first century ad onwards. Both feature medium grain size and a white‐greyish colour with black patches. In order to obtain a certain microscopic and geochemical discrimination of these rocks, and to provide the first known petrographic classification of the ‘Granito di Nicotera’, a comprehensive mineralogical, petrographic and geochemical investigation was performed on several samples from the quarry. The results were compared with the corresponding data known for Marmor Claudianum in the literature. Good discrimination between the granites is possible, mainly on the basis of modal mineralogy and geochemical characteristics. The ‘Granito del Foro’ contains hornblende, while the ‘Granito di Nicotera’ contains muscovite, and has a distinctive peraluminous index and trace element abundances.     

RIETVELD X-RAY DIFFRACTION AND X-RAY FLUORESCENCE ANALYSIS OF AUSTRALIAN ABORIGINAL OCHRES*

Rietveld phase analysis of X-ray powder diffraction patterns and chemical analysis by X-ray fluorescence spectroscopy have been used to characterize a series of red and yellow ochre samples from Aboriginal ochre deposits in South and Western Australia. The ochres were found to have diverse mineralogy, being mixtures of up to seven minerals, and also to have complex trace element signatures. The mineralogical characteristics and geochemistry of the ochres can be used to identify the source quarries. Using this combination of analytieal techniques it may be possible to trace the source of ochres in burial sites and on objects back to the original quarries.     

In the Steps of William the Conqueror: Neutron Activation Analysis of Caen Stone*

Quarries in the Bathonian stone formation surrounding Caen produced high‐quality limestone for medieval churches in northern France and southern England and for their sculptural decoration. To investigate compositional differences among proximate stone sources, 103 samples collected from five separate quarries were analysed by NAA. The results show Caen stone to be essentially pure calcite and relatively homogeneous, but distinction among quarries is possible by discriminant analysis. Comparing compositions of quarry samples with data in the Brookhaven Limestone Database identified the origin of stone used in masonry and sculpture at Saint‐Étienne and La Trinité, Caen, and in several museum objects.     

A New Methodology for the Provenance of Marble Based on EPR Spectroscopy

Fifteen years of research in investigating the characteristics of the EPR spectra of different types of white marble from several quarries in the Eastern Mediterranean has produced an accumulation of a large number of data, and much experience. Statistical treatment of these EPR data (statistical distributions and parameter correlations), has led to the selection of 10 parameters that are useful for quarry discrimination. Apart from the EPR parameters, the maximum grain size, measured with a stereomicroscope, has been found very useful. Boxplots have been found to be very useful as a first easy visual tool for evaluating the discrimination capacity of each parameter. On the basis of these results, a new methodology for determining the provenance of an archaeological sample was developed in stages, using a different pair or combination of parameters each time. In the first stage, the Penteli, Naxos, Hymettus and Proconnessus quarries are completely separated from each other. However, overlapping occurs between the parameter fields of Paros and Proconnessus, Paros and Hymettus and between the two archaic quarries of Melanes and Apollon on Naxos. If the sample is located in a non‐overlapping area, its provenance is obvious and easily determined. If the sample lies in one of the above three overlapping areas, an additional stage is necessary, in which other parameters are used to eliminate or decrease the overlap. Despite the partial overlapping of Paros with other quarries, the famous Lychnites marble of Paros, which was quarried underground, is clearly distinguished.