Zircon

 
Zirconzircon is known since the Middle Ages. The oldest known zircons are from Western Australia, with an age of 4.4 billion years. The name probably comes from the Persian word “zargun” which means “gold-colored,” although zircon comes in a wide range of different colors. The most popular zircon-color is blue.Most blue gemstones come in a pastel blue, but some exceptional gems have a bright blue color. Zircon is also available in green, dark red, violet, yellow, brown, and orange. Due to its high refractive index and strong dispersion, zircon has great brilliance and intensive fire. The luster is vitreous to a brilliant sheen. Although relatively hard (rating 6.5-7.5 on Mohs scale) zircon is brittle and therefore sensitive to knocks and pressure. The gem has the tendency to wear along facet edges. Its use in rings should therefore be limited to protective settings or occasional wear jewelry. Zircon jewelry should be stored carefully.

Zircon is a birthstone for those who are born in December.

 

Zircon colors
Colorless when pure, the zirconium silicate takes on various shades due to impurities. The most popular zircon-color is blue. Most blue gemstones come in a pastel blue, but some exceptional gems have a bright blue color. Zircon is also available in green, dark red, violet, yellow, brown, and orange.
The brown varieties, mostly found in Southeast Asia, are heat treated in order to produce colorless and blue zircons.
In the gemstone trade some terms refer to different colored zircons:
Hyacinth: yellow, yellow-red to red-brown zircon
Jargon: straw-yellow to almost colorless zircon
Starlight: rich, slightly greenish blue zircon variety, created by heating

Buying Zircon
Zircon is brittle and therefore sensitive to knocks and pressure. The gem has the tendency to wear along facet edges. Its use in rings should therefore be limited to protective settings or occasional wear jewelry. Zircon jewelry should be stored carefully.

Color
Medium dark, pure blue stones have the highest per carat value.

Lighting
Zircon looks best in daylight, more precisely: Just after sunrise and before sunset, when the light is considered to be soft and warm.

Clarity
In general zircon is transparent to translucent. Impurities cause the various color. Zircons with a cat’s eye effect are known but rare. Some crystals contain radioactive thorium and uranium. Over time, the radioactivity breaks down the crystal structure so that such stones (usually green) tend to an amorphous structure, with a lower refractive index and luster than the crystalline type. These slightly radioactive zircons are very rare in the trade, but highly prized by collectors and pose no heath threat to its wearer.

Cut
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 brilliant cut. They can fraudulently been offered for “matura” diamond. On the other hand, natural zircon can be confused with synthetic cubic zirconia, a common diamond look-alike. Colored stones get a brilliant or step (emerald) cut.

Round stones are often given a “zircon” cut which is similar to a standard round brilliant cut with an extra row of facets at the edges.

Zircon location and deposits
Zircon deposits are mainly alluvial. Zircon is found in Australia, Brazil, Cambodia, Korea, Madagascar, Mozambique, Myanmar, Nigeria, Sri Lanka, Tanzania, Thailand and Vietnam.

Common Zircon treatments
The brown varieties, mostly found in Southeast Asia, are heat treated at temperatures of 800-1000 degrees C (1472-1832 degrees F), in order to produce colorless and blue zircons. These colors aren’t necessarily stable. Ultraviolet rays or sunlight can produce changes.

World-famous Zircon
If one considers fame the difference between average and elite, zircon indeed has some fame of its own. It is one of the densest gemstones, which means that it will look smaller than other varieties of the same weight.

Zircon gemology
Species: Zircon
Color: Colorless, yellow, brown, orange, red violet, blue, green
Chemical composition: ZrSiO4 zirconium silicate
Crystal system: (Tetragonal), short, stocky, four-sided prisms with pyramidal ends
Hardness: 6.5-7.5 (Mohs scale)
Specific gravity: 3.93 – 4.73
Refractive index: 1.810 – 2.024
Birefringence: +0.002 to +0.059
Color of streak: White,
Absorption spectrum: 691, 689, 662, 660, 653, 621, 615, 589, 562, 537, 516, 484, 460, 433
Fluorescence: Blue: very weak; light orange red and brown: weak, dark yellow

The Zircon zodiac, myth & legend
Zircon is a birthstone for those who are born in December.

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.

In Antiquity, as well as in the Middle Ages one believed that the cosmos reflects in the gemstones. The zircon is assigned to planet Pluto. The esoteric movement revived the ancient believe and the gem industry made it another marketing tool to promote certain gems.

The healing powers of gems remain a controversial issue, but are mentioned for centuries by healers, shamans and medicine men. Whether it’s a fact or a placebo effect doesn’t matter, if it helps. The safest approach is to wear the gemstone in skin contact to the troubled part of the body. Zircon is said to be of help for varicose veins, blisters and testicles problems.