On-Site Raman Spectroscopic Study of Beads from the Necropolis of Vohemar, Northern Madagascar (>13th C.)

In the late 19th century, ancient tombs were discovered near the village of Vohemar at the northeastern point of Madagascar, and subsequent excavations during the French period (1896-1945) revealed the presence of a major necropolis active from similar to 13th to 18th centuries. Some artefacts (Chinese ceramic shards and glass trade beads) recovered from these excavations was sent to France and now in part belong to the collection of the Musee d'Histoire Naturelle, Nimes. Carnelian and glass trade beads were analyzed with a mobile Raman spectrometer, which identified different materials (soda-lime glass, quartz/moganite, carnelian/citrine, chalcedony) and coloring agents (Naples yellow, cassiterite, amber chromophore, transition metal ions, etc.). The results are compared with those obtained on beads excavated at different sites of Southern Africa and at Mayotte Island, and it appears that (most of) the beads come from southern Asia and Europe. The results confirmed the role that northern Madagascar played within the maritime networks of the Western Indian Ocean during the 15th-16th century.