Vincent Serneels

Sulfur isotope analysis of cinnabar from Roman wall paintings by elemental analysis/isotope ratio mass spectrometry – tracking the origin of archaeological red pigments and their authenticity

The most valuable pigment of the Roman wall paintings was the red color obtained from powdered cinnabar (Minium Cinnabaris pigment), the red mercury sulfide (HgS), which was brought from mercury (Hg) deposits in the Roman Empire. To address the question of whether sulfur isotope signatures can serve as a rapid method to establish the provenance of the red pigment in Roman frescoes, we have measured the sulfur isotope composition (δ(34)S value in ‰ VCDT) in samples of wall painting from the Roman city Aventicum (Avenches, Vaud, Switzerland) and compared them with values from cinnabar from European mercury deposits (Almadén in Spain, Idria in Slovenia, Monte Amiata in Italy, Moschellandsberg in Germany, and Genepy in France). Our study shows that the δ(34)S values of cinnabar from the studied Roman wall paintings fall within or near to the composition of Almadén cinnabar; thus, the provenance of the raw material may be deduced. This approach may provide information on provenance and authenticity in archaeological, restoration and forensic studies of Roman and Greek frescoes.

Reconstructing the geomagnetic field in west africa: first absolute intensity results from Burkina Faso

We present absolute geomagnetic intensities from iron smelting furnaces discovered at the metallurgical site of Korsimoro, Burkina Faso. Up to now, archaeologists recognized four different types of furnaces based on different construction methods, which were related to four subsequent time periods. Additionally, radiocarbon ages obtained from charcoal confine the studied furnaces to ages ranging from 700–1700 AD, in good agreement with the archaeologically determined time periods for each type of furnace. Archaeointensity results reveal three main groups of Arai diagrams. The first two groups contain specimens with either linear Arai diagrams, or slightly curved diagrams or two phases of magnetization. The third group encompasses specimens with strong zigzag or curvature in their Arai diagrams. Specimens of the first two groups were accepted after applying selection criteria to guarantee the high quality of the results. Our data compared to palaeosecular variation curves show a similar decreasing trend between 900–1500 AD. However, they reveal larger amplitudes at around 800 AD and 1650 AD than the reference curves and geomagnetic field models. Furthermore, they agree well with archaeomagnetic data from Mali and Senegal around 800 AD and with volcanic data around 1700 AD.

Technological aspects of an early 19th c. English and French white earthenware assemblage from Bern (Switzerland)

Ceramic material from the Brunngasshalde town-waste-dump of Berne, the capital of Switzerland (infilling 1787 - 1832) encompasses 9.2 % white earthenware. Only 1 % of the latter bear impressed stamps of English, French and Swiss manufactures. All stamped English (WEDGWOOD, n=3) and French (CREIL, n=2; NIDERVILLER n=1) material was analyzed by XRF, XRD, MEB-BSE and MEB-EDS. The Wedgwood pottery is rich in coarse SiO 2 grains, interpreted as crushed flint fragments, with abundant signs of a high temperature treatment. They lay in a finely grained siliceous-aluminous matrix, in one specimen together with grog. The Creil material is very similar, but lacks grog. The English white earthenware has lower SiO 2 (73-76 wt. %) as Creil (77-79 wt. %), similar Al 2 O 3 (18-22 wt. %), but more K 2 O (ca. 1 vs. 0.4 wt. %) and Ba (200-220 ppm vs. 130 ppm). In comparison, previously analyzed early French white earthenware from Paris (n=5), produced in Pont-aux-Choux (c. 1750-1788), bearing the characteristic rice grain decoration, differs clearly in its concentrations of SiO 2 (60-61 wt. %) and Al 2 O 3 (32-34 wt. %). Creil and Wedgwood sherds must be classified as siliceous-aluminous white earthenware. The CaO-rich (17 wt.%) Niderviller fragment pertains to the calcareous white earthenware group. A comparison with 19 already published calcareous bodies from Lorraine shows similarities (crushed SiO 2 grains and lead frit as temper in a fine grained siliceous aluminous matrix), but its chemical composition differs from the published analysis of an object stylistically attributed to Niderviller. White earthenware glazes from Niderviller, Paris and the Wegdwood manufacture are transparent lead alkali glazes, and from Creil lead glazes. Niderviller has a K 2 O rich (5 wt. %) and Wedgwood an Al 2 O 3 rich (5-8 wt. %) glaze. Chemical elements diffused from the body to the glaze (e. g. lead) and conversely (e. g. alumina). All samples are artificial bodies, made from a white-firing clay, to which were added ground flint, calcined or not, with or without grog, or ground flint/quartz sand, calcined or not, and lead frits and chalk for the calcareous white earthenware. These results are in good accordance with old recipes. They are also the first archaeometric study of undoubtly (trademark!) Creil, Niderviller and Wedgwood tableware.

Contrasting recipes for the kiln furnitures of the faience manufacture Granges-le-Bourg (Haute Saône, France)

Thirty-nine samples of kiln furniture or technical ceramic (firing plate, saggars, spacers, props, wads) and six samples of building ceramics (bricks, tiles) from the manufacture of Granges-le-Bourg were studied by optical microscopy, X-ray fluorescence, X-ray diffraction and scanning electron microscopy. The kiln furniture is chemically inhomogeneous and belong to a CaO+ MgO-poor (firing plate, saggars) or a CaO+ MgO-rich (props, spacers, wads) group. Bricks and tiles pertain to the first group, which was manufactured using decarbonatized top layers of local Triassic dolomitic marls. For the second group, the deeper layers were used. Plate and saggars are covered with a tin oxide opacified glassy coating with no significant reaction zone to the body.

The massive production of iron in the Sahelian belt: Archaeological investigations at Korsimoro (Sanmatenga – Burkina Faso)

ABSTRACT The large smelting site of Korsimoro was investigated during two fieldwork campaigns in 2011 and 2012. Four different technical traditions are identified. Each is characterized by the spatial organization of the working area, the architecture of the furnace, and the assemblages of wastes. Each technical tradition corresponds to one chronological phase. Phase KRS 1 lasted between 600 and 1000 AD and is characterized by small-scale production. Phases KRS 2 and 3, between 1000 and 1450 AD, showed a very significant increase of the production with an important impact on the organization of the society. There is a collapse of the industry at the time of the installation of the Nakomse conquerors followed by a recovery of the production at a small scale during the 17th century.