The properties of a volcanic ash glass obtained from the Eyjafjallajökull eruption of 2010 were studied. Crystallization experiments were carried out on bulk and powdered glass samples at temperatures between 900 and 1300 °C. Iron oxides, Fe₃O₄ and Fe₂O₃, and a silicate plagioclase, (Na,Ca)(Si,Al)₄O₈, were observed. Bulk samples remained mostly amorphous after up to 40 h at temperature. Powdered glass samples showed increased crystallinity after heat treatment compared to bulk samples. The average coefficient of thermal expansion of the glass was 7.00 × 10⁻⁶ K⁻¹ over 25–720 °C. The Vickers hardness of the glass was 6–7 GPa and the indentation fracture toughness, 1–2 MPa √m Values for density, elastic modulus, and Poisson’s ratio were 2.52 g/cm³, 75 GPa, and 0.24, respectively. The viscosity of the glass was determined experimentally and compared to three common models from the literature. The implications for the deposition of volcanic ash on hot section components of aircraft turbine engines are discussed.