Zircon is a colorful gem with high refraction and fire that’s unfairly confused with cubic zirconia.
Colorless zircon is known for its brilliance and flashes of multicolored light, called fire. These zircon properties are close enough to the properties of diamond to account for centuries of confusion between the two gems.
Zircon occurs in an array of colors. Its varied palette of yellow, green, red, reddish brown, and blue hues makes it a favorite among collectors as well as informed consumers.
Colorless zircon is well known for its brilliance and flashes of multicolored light, called fire. These two zircon properties are close enough to the properties of diamond to account for centuries of confusion between the two gems.
Zircon occurs in an array of colors. Its wide and varied palette of yellow, green, red, reddish brown, and blue hues makes it a favorite among collectors as well as informed consumers.
Zircon crystals grow in many different types of rock and possess a range of optical and physical properties.Some zircons—usually green ones—display much lower values for these properties than others. Scientists have determined that the crystal structures of these gems were almost completely broken down by radioactive elements—often present in zircon as impurities—that damaged the gems’ crystal structure over long periods of geological time.
Some gemologists classify zircons into three types—high, intermediate, and low. A zircon’s classification depends on its properties, which are directly related to the amount of radiation-induced damage done to its crystal structure.
High or normal zircons have full crystal structures, with little or no damage from radioactive elements. As a result, they have the normal physical and optical properties associated with the mineral.
In intermediate or medium zircons, radioactive elements have caused some structural damage. They have physical and optical properties that are between high and low types.
Extensive crystal-structure damage from radioactive elements results in low zircons with much lower optical and physical properties. In extreme cases, they are practically amorphous, which means they lack an orderly crystal structure.
Virtually all the zircons used in jewelry are of the high type. Interestingly, radiation-induced crystal-structure breakdown can be reversed somewhat by heating zircon to high temperatures. High-temperature heat treatment repairs the stone’s damaged crystal structure.
BIRTHSTONES & ANNIVERSARIES
Zircon is a birthstone for the month of December, along with turquoise and tanzanite.
WHY WE LOVE THIS GEMSTONE
GEOLOGICAL CLOCK:With radioactive trace elements that tick off time, zircon is a geological clock that tells us about the early earth.
BRILLIANCE AND FIRE: Zircon has very high luster, refractive indices, and dispersion, giving it lots of brilliance and rainbow flashes of fire.
DOUBLE-DOUBLE :Zircon’s pronounced double refraction means you can see twice as many facets and twice as much fire.
COLOR: Blue, red, yellow, orange, brown, green
HIGH: 1.925 to 1.984 (+/- 0.040)
MEDIUM: 1.875 to 1.905 (+/- 0.030)
LOW: 1.810 to 1.815 (+/-0.030)
BIREFRINGENCE: 0.000 to 0.059 (low to high)
SPECIFIC GRAVITY: 3.90 to 4.73
MOHS HARDNESS: 6 to 7.5 (low to high)