Zircon Gemstone Information

Zircon is not a very well-known gemstone, but it is one of the most important gemstones of today. Many people confuse zircon with the artificial diamond simulant, cubic zirconia. Of course, the two are completely different - cubic zirconia (CZ), is a lab-created synthetic material, while zircon is a naturally occurring gemstone with a very different chemical composition. However, before the introduction of diamond simulants like cubic zirconia and moissanite, white zircon was actually one of the most popular diamond substitutes, owing to its high dispersion and refractive index, and was often marketed under the misleading trade name of 'Matura diamond'. Zircon is also remarkably dense and exhibits a very pronounced level of birefringence. Zircon has such high birefringence that it may appear fuzzy or display facet-doubling.

Zircon occurs in a wide range of colors, of which white or colorless is likely the least valuable or important. The most popular zircon today is blue zircon, usually occurring with green pleochroism, which can result in interesting teal-like colors. Blue zircon is actually produced by heating more commonly occurring brown zircon. However, only some brown materials have the appropriate physical structure to turn blue when heated, typically only deposits found in South East Asia - which is why most blue zircon comes from Cambodia or Burma. Blue zircon is one of the traditional modern birthstones for December.

Zircon is a tremendously important mineral, indeed its prominence led to the emergence of the discipline of 'zirconology' in gemology. It is the oldest mineral on Earth, with samples found in Australia that are over 4.4 billion years old. Scientists discovered that zircon actually contains trace elements of uranium and thorium, both of which are elements with known half-lives. It is the uranium and thorium that cause such tremendous variations in the physical properties of zircon. Zircon is typically classified as low, medium and high zircon, in reference to the presence of optical properties. Low zircon has higher traces of radioactive uranium and thorium, which causes an alteration in physical structure, rendering it near-amorphous, though its physical appearance remains the same as high or medium zircon. Low zircon is typically green to brownish in color. Green zircon is rarely seen in the gem trade and is highly sought after.

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Zircon Stone Click to enlarge

Zircon is actually the oldest known mineral on Earth; the oldest samples are even older than the moon, which formed about 4 billion years ago. Zircon was the first crystal to form in molten granite as it cooled to form rock. Low zircon formed as the result of a process associated with the presence of uranium and thorium. The natural radioactivity disrupts the crystal structure and produces the changes in color and density through a process known as metamictization.

Most zircon deposits are alluvial. Sri Lanka is the best known source for green metamict 'low' zircon. Specimens are also found in Burma (Myanmar), and may possibly exist in other well-known zircon deposits in Cambodia. Most zircon deposits come from Burma, though Australia boasts the oldest deposits dating back more over 4.4 billion years. Other notable sources include Brazil, Korea, Madagascar, Mozambique, Nigeria, Tanzania, Thailand and Vietnam.

Zircon Color

Zircon in its purest form is completely colorless (white), but owing to trace impurities, it can occur in a wide range of interesting colors, including yellow, orange, red, green, blue, violet, brown and combinations in between. Yellow-brown to orange and red zircon are the most common occurrences, along with colorless. Blue is the most popular, but its color is obtained through the heating of brown zircon, usually from Cambodia and Burma. Due to pleochroism, blue zircon can look greenish from certain angles. Medium dark, pure blue stones have the most value. Green zircon is very rare and typically very expensive.

Zircon Clarity and Luster

In general, zircon is transparent to translucent. Impurities cause the various colors. Zircon with cat's eye chatoyancy is known but very rare. Some crystals contain radioactive elements of thorium and uranium. Over time, the radioactivity breaks down the crystal structure so that such stones tend to a near-amorphous structure, with a slightly lower luster than the crystalline form. These low green zircon specimens are rare and are highly prized by gem collectors. They pose no radioactive heath threat. Zircon exhibits a brilliant, vitreous sheen when polished.

Zircon 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; otherwise the interior may look fuzzy, due to facet image doubling. Colorless stones are most often brilliant cut. Colored stones are most often brilliant or emerald step cut. Round stones are often given a 'zircon cut', which is similar to a standard round brilliant cut, but with an extra row of facets at the edges. The most popular shapes include ovals, rounds, pears, octagons (emeralds) and fancy trillions. Small melees are also popular.

Zircon Treatment

Many zircon stones are completely untreated. Some brown varieties, mostly found in Southeast Asia, may be heated to produce colorless and blue zircon. These colors aren't necessarily stable, since ultraviolet rays or sunlight can cause color loss or changes. Some colors are unenhanced, including rose and rose-orange zircon from Tanzania, and orange to orange-brown zircon from Cambodia. Green zircon is very rare and owes its color to minute natural traces of uranium and thorium. Golden-yellow zircon is sometimes heated.

Please refer to our Gemstone Glossary for details of gemology-related terms.

Hyacinth Zircon

Zircon belongs to the large group of minerals known as neosilicates that contain both silicon and oxygen in their composition. The neosilicate group includes varieties of beryl and garnet, andalusite, kyanite, olivine (peridot), tanzanite, topaz, tourmaline and quartz. Zircon is also a primary ore of the element zirconium, a lustrous white-gray metal which closely resembles titanium. Zircon is often confused with the synthetic or lab-grown diamond stimulant known as CZ, or cubic zirconia, but zircon is a natural diamond substitute rather than an artificial simulant. In fact, colorless zircon was at one time a very popular natural diamond substitute, often marketed under the misleading trade name of 'Matura diamond'. It may also be associated with 'moissanite', another popular diamond substitute.

Like sapphire and tourmaline, zircon is often traded using color descriptive names, such as blue zircon, golden zircon and white zircon. There are also some trade names used today for specific color zircon. Some popular names include 'hyacinth' - a historical name that has been used for yellow and golden colored zircon. Golden to red-brown zircon may also be traded as 'jacinth'. In some cases, heated blue zircon may be traded as 'starlight zircon'. 'Jargon' is another name which may refer to pale-yellow to near-colorless zircon. Green zircon is sometimes known as 'metamict zircon' and is actually quite rare.

Zircon is an official birthstone for those who are born in December. It has been treasured since the Middle Ages and times of antiquity, although typically under various other historical names, such as jacinth and hyacinth. The name 'zircon' is thought to be derived from the Persian word "zargun" which means "gold-colored". Hindu poets wrote of the "kalpa tree", the ultimate gift to the gods, which was a glowing tree covered with gemstone fruit with leaves of zircon.

In the middle ages, zircon was said to aid sleep, bring prosperity, and promote honor and wisdom in its owner. Since ancient times, it has been believed that the cosmos is reflected in gemstones. Zircon is assigned to the planet Pluto. Zircon is said to be of help for varicose veins, blisters and testicle problems.

Zircon is brittle and therefore is sensitive to knocks and pressure. However, it has good hardness and durability. The gem has the tendency to wear along facet edges owing to its brittle tenacity, so its use in zircon rings, should be limited to protective style settings or occasional wear jewelry. Most zircon stones are small in size, due to their dense nature, but some rare large stones can be found. Larger stones are excellent for bold designs, such as unique pendants or brooches. Blue zircon is very popular for rings and earrings, and colorless zircon is often used in bridal jewelry as a diamond substitute. Owing to its versatility in color availability, zircon gemstone jewelry can be ideal for both men's, women's and children's designs.

Note: Buy colored gemstones by size and not by carat weight. Colored stones vary in size-to-weight ratio. Some stones are larger and others are smaller than diamonds by weight in comparison.

If one considers fame the difference between the average and the exceptional, zircon indeed has some fame of its own. It is one of the densest gemstones, which means that it will look smaller than other gem types of the same weight. It is about 50% denser than diamond - if you have a diamond and a zircon of similar size, if the diamond weighs 1 carat, the zircon will weigh about 1.5 carats.

Zircon is rather durable with its good hardness and indistinct cleavage, but its brittle tenacity can cause fractures and chips, especially along facet edges requiring extra care when setting, cleaning or wearing. Avoid steamers or ultrasonic cleaners when cleaning zircon gems and jewelry, particularly with stones that may have been color-enhanced. Avoid the use of harsh cleaning chemicals or agents, especially bleach and acid. You can wipe down stones using a soft cloth or brush and a mild soap or detergent if needed. Be sure to rinse your stones well using warm or room-temperature water to remove soapy residue.

Always remove jewelry when engaging in any type of physical activity, including household chores, exercise or sports. It is best to store gems and jewelry separately from one another to prevent scratches and fractures. When storing zircon gemstones, it is best to wrap them in a soft cloth or place them inside a fabric-lined box.