As an optical method, Raman microspectroscopy offers a great advantage over most other techniques in that it can be performed without any contact with the studied artefact, both at the laboratory using highresolution, large spectral window instruments, and on site using medium resolution, portable instruments. Six years of experience on various materials has enabled us to propose a tentative guide to identify different types of glassy silicates and to classify them as a function of their composition. In previous papers, different families were recognised empirically using a limited set of samples and the relationship between the peak area ratio (A 500 /A 1000 ) of the Si-O bending (∼500 cm −1 ) and stretching (i.e. ∼1000 cm −1 ) envelopes, and the different components of the latter peak were established for porcelain glazes. In this paper, we extend the procedure to a larger set of samples (30 representative samples with known compositions selected from hundreds of spectra). Additional relationships between the origin of the material, the Raman parameters and the glass composition (fluxing oxide content, ionicity ratio, etc.) are discussed. Finally we propose different procedures with different degrees of complexity (from two to multivariate treatment) to identify the glass composition. The method is illustrated with an example, namely, the differentiation between Iznik and Kütahya productions.

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Iron archaeological artefacts were studied to understand long-term corrosion by the atmosphere. Indeed, these samples collected on the construction elements of ancient monuments present ancient rust layers formed during their exposure over centuries to the indoor atmosphere. Thanks to Raman spectroscopy and the acquisition of hyperspectral images of the corrosion scales, several zones of the samples observed on cross sections could be characterised. It has been shown on six dated samples that the main phase is goethite (a-FeOOH). Lepidocrocite and akaganeite (g-FeOOH and b-FeOOH) occur locally in the corroded products, often correlated with cracks. A less crystallised phase, a hydrated oxy-hydroxide, has been identified abundantly in more or less extended zones inside the layer. This phase could play an important role in atmospheric corrosion mechanisms.

The description and identification of corrosion products formed on archaeological iron artefacts need various approaches at different observation scales. For this study, samples from five sites were prepared using two techniques. The first consists in cutting cross-sections perpendicular to corrosion layers. This allows local observations and analysis of the corrosion layer stratigraphy at different levels. The second consists in performing manual grinding or abrading of the corrosion layers starting from the current surface of the excavated artefact to the metal core. It allows the description of the successive layers and is well adapted for the analysis on a larger scale. In addition to these two observation scales, the identification of the iron oxides formed needs the coupling of several complementary techniques. Elementary compositions were determined by scanning electron microscopy-energy-dispersive x-ray (SEM-EDX) analysis and electron probe microanalysis (EPMA). Structural identification was performed by x-ray micro-diffraction under synchrotron radiation (µXRD) and micro-Raman spectroscopy. These analyses were performed on the same samples with both x-ray diffraction and Raman spectroscopy in order to ensure a reliable characterization. In some cases there are some ambiguities or overlapping between signatures of different phases by µXRD (such as maghaemite-magnetite) or Raman spectroscopy (such as goethite-magnetite) which can be overcome by the association of the two methods. The final aim is to set up an analytical methodology that will be optimal for the study of ancient iron corrosion products. It is the first step in the study of long-term mechanisms of iron in soil.