THE GOLD OF THAT LAND: Biblical Minerals & Rocks  

68.     zircon

Greek: huakinthos, derived from the Greek kuanos, deep blue. A gem of hyacinthine or deep blue color. Revelation 21:20.

Arabic: zarqûn, golden color.

Probable Identification: huakinthos is probably turquoise or lapis lazuli.

Mineralogy:

    Hyacinth is the modern term for an orange variety of gem zircon. The derivation of the Greek word points to lapis lazuli or turquoise as a more likely choice for the biblical precious stone because both were both highly valued for their blue color in the ancient world.

    Clear zircon or zirconium silicate (ZrSiO₄) comes close to diamond in luster and fire, but falls well short in hardness. Zircon forms prismatic tetragonal crystals with bipyramidal terminations. Zircon is usually brownish and translucent, but gem crystals range in color from clear to red, yellow, green, blue, and black. Heat treatment changes reddish zircons into clear white or very pale yellow stones known as "jargoon" or "jargon."

    Zircon has a hardness of 7 to 7.5, a specific gravity between 4.6 and 4.8, and tends to be brittle. Most igneous rocks contain tiny, scattered zircon crystals, but gem-class zircons crystallize in granites and pegmatites in association with quartz, tourmaline, and beryl. Transparent red and brown gem zircons come mostly from gravels in Thailand and the nearby Kha district of Vietnam. These deposits represent the concentrated residues of weathering from granite. Other sources are Burma, Ceylon, Madagascar, the Ural Mountains, and Australia.

    In addition to its inertness and high melting point, zircon may incorporate atoms of certain radioactive elements into its crystal structure. Uranium atoms are so nearly equal to zirconium atoms in diameter that they easily take their place in a zirconium crystal. Radioactive uranium isotopes serve as built-in radioactive clocks. The ratio of radioactive uranium to its decay products enables geologists to determine how long ago a zircon crystal formed.

    Zircon’s chemical inertness and high melting point also make it useful today in making refractory brick and special ceramics. Rich concentrations of zircon grains in beach sands are the principal source of the metals zirconium, element 40, and hafnium, element 72.

    Cubic zirconia (ZrO₂) is a synthetic gemstone.

Sources:

http://science.howstuffworks.com/atomic-clock1.htm

Hurlbut, 1952, op. cit.; 391-392.

_____, 1970, op. cit.; 63.

Kröner, A, M. Eyal, & Y. Eyal, 1990. Early Pan-African evolution of the basement around Elat, Israel, and the Sinai Peninsula revealed by single-zircon evaporation dating, and implications for crustal accretion rates. Geology; 18: 545-548.

Los Alamos National Laboratories. http://periodic.lanl.gov/elements/40.html

Mathez, Edmond A., 2004. A birthstone for Earth. Natural History; 113-4: 40-45.

Ralph, Jolyon, 1993-2004. http://www.mindat.org/min-4421.html

Schumann, op. cit.; 109-109.