Determination of iron environment and redox in heterogenous obsidians

Obsidian, a prevalent naturally occurring glass formed through rapid cooling of rhyolitic lava, holds significance in earth and material sciences, as well as archaeology. While black obsidian is widely recognized, lesser-known variants exhibit diverse colors such as green, blue, red, brown, and silver, whith often heterogeneous mixing areas. Iron, a key component in obsidian, plays a crucial role in coloration. In black obsidian, dispersed iron nanocrystals contribute to its distinct color and rheological properties To unravel the relationships betwwen iron environment/redox and color/rheological properties, nano-XANES emerges as a crucial tool, enabling the investigation of iron speciation at the nanoscale. This approach aims to discern the precise environment, redox state of iron, and its impact on color variation in crystallized and non-crystallized areas of heterogeneous obsidians.