ZIRCON

Zircon is a colorful gem with high refraction and fire that’s unfairly confused with cubic zirconia.

OVERVIEW

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.

WHERE IS IT FOUND ?

Sri Lanka’s wealth of gems is legendary: Sapphire in various colors, ruby, alexandrite, spinel, tournamline, moonstone and quartz are some of the gem minerals unearthed there. So is the December birthstone zircon. Elahera, a region in central Sri Lanka, is one of the country’s most productive areas. Mountains, jungles and restless streams make for a dramatic landscape.

Australia’s Harts Range is known for producing zircon birthstones in yellow-brown, orangy brown, pink and purple. Go there and you’ll see open savannahs, dry stream beds and low-lying hills that meet the horizon. Zircon Hill is where this December birthstone is mined. The nearby city of Alice Springs is known for its outback culture, aboriginal art and quirky sporting events like a regatta race held in a dry river bed.

This December birthstone is often located near sapphire sources. In addition to Sri Lanka and Australia, countries where the two gems overlap include Myanmar, Vietnam and Cambodia.

CARE & CLEANING

Zircon ranges from 6 to 7.5 on the Mohs scale of hardness. It is commonly heat treated to produce blue and colorless varieties, as well as orange, yellow and red. The gem is generally stable when exposed to light, but some heat-treated stones may revert to their original colors (usually light brown) after prolonged exposure to bright light. Exposure to heat can alter the color of some zircon. This December birthstone is stable when exposed to chemicals.

Because zircon tends to abrade, it is best to avoid wearing it in rough conditions, such as while gardening, playing sports or doing dishes.

Clean your zircon using a soft brush and mild soap in warm water. Ultrasonic and steam cleaners are not recommended for this December birthstone.

Turquoise, tanzanite and zircon – you can choose from so many shades of blue when you’re born in December. You’ll also be able to pick gems that are bright red, yellow, green, purple and brown. Have fun looking for the perfect December birthstone that reflects your personality.

HISTORY

Many people have heard of zircon but never seen it. This is mostly because of colorless zircon’s wide use as a diamond simulant in the early 1900s. It was long ago replaced in that role by more convincing look-alikes, but its name still means “imitation” to many people. That’s unfortunate because zircon is a beautiful colored stone with its own fair share of folklore and charm.

In the Middle Ages, this gem was thought to induce sound sleep, drive away evil spirits, and promote riches, honor, and wisdom.

Many scholars think the stone’s name comes from the Arabic word zarkun, meaning “cinnabar” or “vermilion.” Others believe the source is the Persian word zargun, or “gold colored.” Considering zircon’s color range, either derivation seems possible.

Blue zircon was a particular favorite in Victorian times, when fine gems were often featured in English estate jewelry dating from the 1880s. Gemologist George Kunz—Tiffany’s famed gem buyer—was a notable zircon advocate. He once proposed the name “starlite” to promote the gem’s fiery nature. The name never caught on.

BIRTHSTONE

Zircon is a birthstone for the month of December, along with turquoise and tanzanite.

FACT SHEET

Mineral: Zircon
Chemistry: ZrSiO4
Color: Blue, red, yellow, orange, brown, green
Refractive index:
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)

Source of Content : www.gia.edu