Resistivity of obsidians based on Figure seven in Gaillard (2004). Diamonds denote laboratory measurements of resistivity for hydrous obsidians. Red and blue lines are estimated resistivity based on the Arrhenius law. The resistivity of dry obsidian (black line) is calculated from the results of different pressure conditions. The green dashed line denotes the resistivity range of the C-2 and C-3a conductors.