Crystalline, brittle metal, with reddish tinge. Soluble in nitric and hydrochloric acids. Highly diamagnetic (mass susceptibility -1.35 X 106). Expands 3.3% on solidification.  Electrical resistivity higher in solid than in liquid state. Extrudable at 437 oF, not fabricable at room temperature. Brinell hardness 7. Thermal conductivity is lowest of all metals except mercury. On heating it burns to form the oxide