- a gray, toxic metallic element with a high melting point (over 2000°C), found in most zirconium minerals. Symbol: Hf; atomic weight: 178.49; atomic number: 72; specific gravity: 12.1.
- a bright metallic element found in zirconium ores: used in tungsten filaments and as a neutron absorber in nuclear reactors. Symbol: Hf; atomic no: 72; atomic wt: 178.49; valency: 4; relative density: 13.31; melting pt: 2231±20°C; boiling pt: 4603°C
