Zircon – a gemstone with charisma
Zircons are minerals and, in addition to zirconium and silicon dioxide, they also consist of radioactive accompanying elements. Hafnium, uranium or thorium are among those radioactive elements that occur in zircons to a minimal extent.
There is no reason for concern: the outgoing radiation of most stones is so low that it does not even reach the human skin, let alone penetrate the first layer of skin.
High, medium and low zircon
Over millions of years, the radiation inside the zircon breaks down its crystal structure. This changes its color, luster and hardness.
High-grade zirconia are usually colorless or have a slightly whitish or bluish tinge. Some high-quality zirconia have a brownish-orange color. These stones are completely crystalline – the atoms and molecules form a robust crystal lattice due to their arrangement. They also have a Mohs hardness of about 7.5 and are birefringent.
Medium zircons have already been exposed to radioactive radiation for a long time and therefore have a damaged crystal structure. Most of these zircons are green-brown to dark red. Their Mohs hardness is around 7. Like the high zircons, they are still birefringent.
Deep zircons are amorphous – the atoms and molecules no longer have a structured composition. That is why these zircons only have a hardness of 6 to 6.5 and are only simple refractive. In most cases, they are therefore cloudy. The color spectrum ranges from green to orange to a dark brown.
Well-known diamond substitute
Zircons have been very popular for a long time: since they are also available in colorless varieties, they are an excellent substitute for diamonds – provided they are well cut. With the right cut, laymen can hardly tell the difference between zircons and diamonds.
Interesting fact: colorless high-zircons are even rarer than diamonds, yet they cost less.
Synthetic zircon: cubic zirconia
In the 1930s, artificial stones were made from cubically stabilized zirconium oxide for the first time – known as “cubic zirconia”. Mass production of the stones began in the mid-1970s.
Since the term “zircon” was also used for cubic zirconia, the real gemstone has had a bad image over the last few decades. However, this has since recovered and the blue zircon (starlit) in particular is enjoying growing popularity.
Use
Zircons are – as already mentioned – a substitute for diamonds. They sparkle just as beautifully and usually cost only a fraction. However, since they are not as hard as diamonds, they should be used with caution in rings. Otherwise, the stones can splinter all too easily.
According to the American Gem Society, blue zircon is the modern birthstone for the month of December, along with blue topaz and tanzanite. Traditionally, lapis lazuli or turquoise are also among the birthstones for those born in December. The stone symbolizes wisdom, trust and prosperity. Blue zircon is also said to have sleep-inducing properties.
Blue or colorless zircons are often processed together with blue sapphires, as the colors accentuate each other. A pendant with these two gemstones on a chain made of white gold or silver is guaranteed to be an eye-catcher.
Origin & mining sites
The name of the gemstone comes either from the Persian word zargun (gold-colored) or from the Arabic zarqun, which means “cinnabar”.
Zircons are a separate mineral group. The term hyacinth was already used in ancient times for a mineral with a bluish to violet color. The stone has been represented in mineralogy as a zircon since 1783.
Since zircon is a mineral, it can be found in volcanic rock all over the world – particularly in granite. However, a large number of high-quality gemstones can be found in Southeast Asia, especially in Sri Lanka.
Cambodia and Myanmar also have large deposits of zircon, some of which have already undergone heat treatment to change the color of the stones.
Properties
Zircon forms its own mineral group. The oldest zircons found to date have been determined to be 4.4 billion years old, making zircon the oldest mineral on earth.
On the Mohs scale, zircons reach a hardness of 6 to 7.7, depending on their age and the radiation exposure inside the stone.
Colors
Zircon is available in different colors: from colorless to green to brown-red tones. Zircons get their names depending on their color. The most well-known types include:
Hyacinth: Hyacinths are yellow, yellow-red or even red-brown zircon varieties.
Starlit: Starlit is characterized by its blue color. This is the result of a special heat treatment to which reddish zircons are subjected.
Jargon: Straw-yellow to colorless stones are usually jargons.
Treatment
Many zircons are heat-treated to obtain the beautiful colors. To do this, reddish-brown zircons are heated to produce blue, colorless or golden yellow zircons. Zircons with other colors are normally not heat-treated.
A tip for gemstone jewelry when buying zircon: zircon that has been heat-treated to turn green or yellow is more resistant to UV rays than zircon that turns blue. If the jewelry is likely to be exposed to a lot of sunlight, it is better to choose green, yellow or natural red stones.
The cut
The stone cutter is particularly challenged when working with zircon because of its brittleness. In most cases, zircon is cut in a brilliant cut and in a modified brilliant cut. Another type of cut used for zircon is the stepped cut.
