Structural Change of a Volcanic Glass (obsidian) under High Pressure

Abstract

High pressure structural change of an obsidian from Iceland has been investigated using X-ray radial distribution function (RDF) analysis and Raman spectroscopy. Obsidians have been compressed under 4 GPa at 20°C and 500°C by a cubic anvil apparatus. The obsidian treated under 4 GPa-20°C condition shows almost the same density and RDF curve as the original obsidian. However, the permanent densification of about 9% was observed by the compression under 4 GPa-500°C Based on RDF and Raman analyses, the structure of obsidian may change in the dominant TO₄ (T=Si and Al) from 5 and 6 to 4 and 3 membered rings by the compression at 500°C.