(Zr,Hf,U,Th,Y)SiO4
and Aggregates
Zircon also occurs as grains, as fibrous aggregates, and as rounded, waterworn pebbles. Twinned Zircon crystals are uncommon.
Cyrtolite - unstable variety of Zircon with traces of radioactive elements in its chemical structure Hyacinth
or Jacinth - yellow, orange, brown, or
red variety of Zircon Jargon
or Jargoon - colorless to pale gray or
pale yellow variety of Zircon
Starlite
- blue variety of Zircon Matarua
or Matara - colorless Zircon used to
resemble DiamondThe dark brown to black color observed in most Zircon crystals is caused from iron oxide impurities. The green coloring in many rounded pebbles usually indicates the Zircon as the radioactive Cyrtolite variety.
Zircon most often occurs in igneous environments, usually in granitic pegmatites. However, it does occur in metamorphic environments, as well as in placer deposits. Most gemstone grade Zircon is from placer deposits, in the form of rounded, waterworn pebbles.
Zircon is a famous gemstone occurring in many colors. Its brilliant luster and fire, combined with its hardness and range of colors makes it a most desirable gem. Almost all Zircon gems are artificially colored by heat-treatment. Many of its gem colors are rarely found naturally in such color. An interesting and strange habit exhibited in only few zircons is that their color darkens and their luster dulls upon prolonged exposure to sunlight. This effect can be reversed by giving the stones a second heat-treatment.
Zircon is often confused with Cubic Zirconia. Cubic Zirconia, a synthetic, inexpensive Diamond simulant, resembles colorless Zircon and has a similar sounding name. However, the two are totally separate materials, and have no connection with each other. Although colorless Zircon may also be used as a Diamond fake, it is still quite valuable in its own right, as opposed to the cheap, synthetic Cubic Zirconia.
Zircon is by far the most important ore of zirconium, and it is also the most important ore of the rare element hafnium, which is often present in considerable quantities in zircon. In several localities, Zircon is also an ore of the radioactive element thorium.
Also see the gemstone section on Zircon
Similar Minerals
Cassiterite - heavier
Spinel - occurs in octahedral crystals, lighter in weight (3.5 - 4.1)
Hafnon - cannot be distinguished without complex tests
Occurs With
Localities
Canada contains many excellent localities for this mineral. Enormous crystals, up to a foot long in a few cases, have been found in Renfrew Co., Ontario. Large crystals also come from Bancroft and Dunngannon, Hastings Co., Ontario, and transparent pink crystals were found in the McLaren Mine, near Perth, Ontario. Large, well formed crystals are famous from Tory Hill, Wilberforce, Haliburton Co., Ontario. Zircon associated with Aegirine occurs in Mont Saint Hilaire, Quebec.
In the U.S., Zircon is found as small, occasionally transparent pebbles on the beach sands of North Carolina, South Carolina, Georgia, and Florida. Perfect, loose crystals are found in the gravel in Henderson Co., North Carolina, and shiny black crystals were discovered in the Eureka Tunnel, St. Peters Dome, El Paso Co., Colorado. Other famous U.S. localities are Sparta, Franklin, and Ogdensburg, Sussex Co., New Jersey; and Bedford, Westchester Co., New York.
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