Zirconium, a metallic element that occurs as a hard, gray, crystalline substance and as a noncrystalline blue-black powder. Because it resists corrosion and has a high melting point, zirconium is used in furnaces, chemical tanks, electrical insulators, and jet engines. It is also used as a covering for fuel rods. The element was discovered in 1789 by the German chemist Martin Heinrich Klaproth.

Zircon, the chief zirconium ore, occurs in transparent, translucent, and opaque forms and may be colorless or yellow, brown, red, or green. Some transparent varieties are valued as gems. Australia accounts for more than half of the world's zircon production. Other major producers are South Africa and the United States.

Symbol: Zr. Atomic number: 40. Atomic weight: 91.224. Melting point: 3,365.6 F. (1,852 C.). Boiling point: 7,911 F. (4,377 C.). Specific gravity: 6.51. Zirconium belongs to Group IVB of the Periodic Table and has valences of +2, 3, and 4.