Competing English, Spanish, and French alabaster trade in Europe over five centuries as evidenced by isotope fingerprinting.

A lack of written sources is a serious obstacle in the reconstruction of the medieval trade of art and art materials, and in the identification of artists, workshop locations, and trade routes. We use the isotopes of sulfur, oxygen, and strontium (S, O, Sr) present in gypsum alabaster to unambiguously link ancient European source quarries and areas to alabaster artworks produced over five centuries (12th-17th) held by the Louvre museum in Paris and other European and American collections. Three principal alabaster production areas are identified, in central England, northern Spain, and a major, long-lived but little-documented alabaster trade radiating from the French Alps. The related trade routes are mostly fluvial, although terrestrial transport crossing the major river basin borders is also confirmed by historical sources. Our study also identifies recent artwork restoration using Italian alabaster and provides a robust geochemical framework for provenancing, including recognition of restoration and forgeries.

Building materials as intrinsic sources of sulphate: a hidden face of salt weathering of historical monuments investigated through multi-isotope tracing (B, O, S).

Sulphate neoformation is a major factor of degradation of stone monuments. Boron, sulphur and oxygen isotope signatures were investigated for five French historical monuments (Bourges, Chartres and Marseille cathedrals, Chenonceau castle, and Versailles garden statues) to investigate the role of intrinsic sulphate sources (gypsum plasters and mortars) in stone degradation, compared to the influence of extrinsic sources such as atmospheric pollution. Gypsum plasters and gypsum-containing mortars fall systematically in the δ(34)S and δ(18)O range of Paris Basin Eocene evaporites indicating the origin of the raw materials (so-called "Paris plaster"). Black crusts show the typical S and O isotope signatures observed elsewhere in Europe that can be attributed to atmospheric pollution, together with a marine component for Marseille. Boron isotopes for black crusts indicate coal combustion as principal boron source. Mortar isotope compositions discriminate three types, one similar to gypsum plasters, one strongly depleted in (34)S, attributed to pyrite oxidation, and a third one close to atmospheric sulphates. The isotopic composition of sulphates and boron of most degraded building stones of the different monuments is well explained by the identified sulphate sources. In several cases (in particular for Chenonceau and Bourges, to some extent for Chartres), the impact of gypsum plaster as building and restoration material on the degradation of the stones in its vicinity was clearly demonstrated. The study illustrates the usefulness of multi-isotope studies to investigate stone degradation factors, as the combination of several isotope systematics increases the discriminatory power of isotope studies with respect to contaminant sources.