Obsidian from yesterday to tomorrow

Obsidian stones have been part of human history for over 10,000 years. They were used to make the first tools of modern man, as well as the first jewels that embellished the lives of our ancestors.

Despite this long history between man and obsidian, many questions remain:

• What are their origins and eruptive dynamics?
• Where do their black, red, green or blue hues come from? Spinel nanoparticles seem to be the source of black obsidian, but what about the other colors? And how are these nanoparticles formed?
• Is it possible to valorize obsidian by manufacturing new materials?

The aim of this thesis project is to characterize obsidian samples from Mexico (Coll. F. Gendron, MNHN), the USA and Turkey. Viscosity measurements will be used to determine their rheological properties. Understanding the origin of the color (role of iron, bubbles, nanoparticles) will be carried out using various methods: optical spectroscopy, SEM and TEM, synchrotron radiation to determine iron redox.

We will then assess the possibility of manufacturing glasses from obsidian: could the first glasses melted by mankind have been obtained from this raw material? Are new compositions possible by mixing recycled glass with volcanic lava? The same questions of rheological properties and coloring of the final product will be addressed with these new glasses. We have at our disposal a corpus of samples from several deposits, which will need to be characterized and prepared for X-ray absorption experiments at the iron K threshold planned on the LUCIA-SOLEIL line.

The thesis work will be carried out at IMPMC, IPGP and IRAMAT-Orléans.
At IRAMAT, elemental analysis will be carried out by LA-ICP-MS on the various obsidian samples and on archaeological objects, in order to identify the various gitologies.
IMPMC will be in charge of color characterization studies using optical absorption spectroscopy, and electron microscopy observation.
Together with IPGP, they will conduct synchrotron studies (SOLEIL, ESRF) to characterize the redox and environment of iron, the main coloring element in obsidian rocks. IPGP will be in charge of obsidian viscosity measurements, Raman spectrometry characterizations and viscosity measurements on the new glasses obtained.