History & Introduction

Zircon is not a very well-known gemstone, still it is one of the most important gemstones at present. Zircon confuse people with the artificial diamond simulant and cubic zirconia. However in practical the two are completely different - cubic zirconia (CZ), is a lab-created synthetic material, whereas zircon is a naturally available gemstone having a different chemical composition. Still before the introduction of diamond simulants such as cubic zirconia and moissanite, due to the property of high dispersion and refractive index white zircon was actually one of the most popular diamond substitutes, and was often marketed under the misleading trade name of 'Matura diamond'. Zircon gemstone is even remarkably dense and shows a very pronounced level of birefringence. Zircon has such high birefringence-facet mirror or screen may appear blurred.

Zircon is produced in a wide variety of colors from which the white or colorless probably is less valuable or important. The most famous stone this time is blue zircon, usually is available with green pleochroism that result in interesting colors like blue-green. When brown zircon is heated, then it result in the production off blue Zircon. However, only few of the brown materials are keyed to turn blue while heated normally available in Southeast Asia that is why most blue zircon comes from Cambodia or Burma physical structure. Blue zircon is one of the traditional modern birthstones for December.

Zircon mineral is extremely important, in fact its importance led to the emergence of the discipline of 'zirconology' in gemology. Zircon gemstone is considered as the oldest mineral on Earth having samples available in Australia which are around 4.4 billion years old. As per the scientists the zircon actually contains trace elements of uranium and thorium, both the elements are known with known half-lives. Due to the uranium and thorium such tremendous variations are caused in the physical properties of zircon. Zircon gemstone is naturally classified as low, medium and high zircon, related with the presence of optical properties. Low zircon is naturally brownish to green in color. Zircon in green is hardly seen in the gem trade and is highly sought after.

Recognize - In composition the gemstone is zirconium silicate. As per its gemological characteristics it displays a great varieties such as hardness ratings spanning from 6.5 to 7.5 on the Mohs scale. Zircon is easily distinguished by its prominent birefringence; when looking down through the table of a stone, the doubling effect of facet edges is easily noticeable. It even carries a high refractive index that ranges from 1.810 to 2.024, with a density ranging between 3.93 and 4.73. Zircon even has a relatively high dispersion rating, showing fire and brilliance comparing with fine diamond.

Availability - Zircon is the oldest mineral found on earth; even older than the moon, the formation is around 4 billion years ago. In fact it is the first crystal to form in molten granite as it cooled to form rock. Sri Lanka is the best deposits of green metamict 'low' zircon. It is also found in Burma (Myanmar), and even in Cambodia. Mainly the deposits of zircon come from Burma, though Australia has the oldest deposits over 4.4 billion years. Other prominent sources are Mozambique, Brazil, Tanzania, Korea, Madagascar, Nigeria, Thailand and Vietnam.

Usages - Zircon available in every colors are used as gems, however golden-brown, blue as well as white are frequently used colors. Blue Zircon available in lively pastel blue is a well-known color and has a rarely striking bright blue color. Colorless Zircon is available in cut that is brilliant to bring out its fire to its fullest. More often it is used as natural alternative to diamond, which is available at lower price. The other color forms (green, yellow, pink and purple) are less used in jewelry.

Buying Guide

Color - Zircon in its purest form is completely colorless (white), however because of the presence of impurities, it occurs in a large variety of interesting colors that adds to red yellow, violet, orange, green, blue, brown and combinations likem Yellow-brown to orange and red zircon are the popular occurrences. Blue is the most popular, but it gets the color by heating of brown zircon. Due to pleochroism, blue zircon looks greenish from certain angles. Medium dark, pure blue stones possess the maximum value. Green zircon is hardly available and is expensive.

Clarity and Lustre - The clarity of zircon is from transparent to translucent. Impurities results in various colors. Cat's eye chatoyancy zircon is famous still very rare. Some crystals have radioactive elements of thorium as well as uranium. With time, the radioactivity breaks down the crystal structure so that such stones are closer to amorphous structure having less luster as compared to the crystalline form. Such examples of low green zircon rare and are highly valued by gem collectors. They have no threat of radioactive heath. Zircon when polished gives a brilliant and vitreous sheen.

Cut and Shape - The high birefringence of zircon makes it necessary for the cutter to orient the table of the stone to the optic axis. Colorless stones are most often brilliant cut. Colored stones are mainly available in brilliant or emerald step cut. Round stones are provided a 'zircon cut' that is similar to a standard round brilliant cut, still having an extra row of facets at the edges. The famous shapes of the gemstone include ovals, fancy trillions, octagons (emeralds), rounds and pears. Small melees are also popular.

Treatment - Many zircon stones are totally not treated. Some brown varieties, available in Southeast Asia are heated to create colorless and blue zircon. However the colors are not necessarily stable because of ultraviolet rays or sunlight that results in the color loss or changes. Some colors are not changed like rose and rose-orange zircon, and orange to orange-brown zircon. Sometime heat is given to golden-yellow zircon.

Gemological Characteristics:

Chemical Formula	ZrSiO4; Zirconium silicate
Crystal Structure	(Tetragonal), short, stocky, four-sided prisms with pyramidal ends
Color	Colorless, orange, yellow, brown, red violet, blue, green
Hardness	6.5 to 7.5
Refractive Index	1.810 to 2.024
Density	3.93 to 4.73
Cleavage	Blurry
Transparency	From transparent to translucent
Double Refraction or Birefringence	0.002 to 0.059
Lustre	From Vitreous to brilliant sheen
Fluorescence	Blue: very weak; light-orange, red and brown: dark-yellow, weak
Mineral Class	Zircon

Classification:

• White zircon
• Colorless zircon
• Blue zircon
• Red zircon
• Green zircon
• Yellow zircon
• Orange zircon
• Brown zircon
• Pink zircon
• Purple zircon
• Gray zircon