Characteristics: Silver-white. Low ductility. Does not tarnish in air. On heating strongly, a slightly volatile oxide is formed. Insoluble in acid, slowly soluble in aqua regia and in fused alkalies. Most corrosion-resistant element, modulus of elasticity is one of the highest. Highly resistant to chemical attack. Toxicity is probably low. Due to the brittle nature of iridium the fabrication of rod requires melting iridium sponge into a cylindrical shaped ingot and grinding to the finish diameter.