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Zircon: the misunderstood stone

Zircon: the misunderstood stone

A zircon miner examines a stone sluiced from the mud.

Its blue can be as attractive and deeply saturated as a top quality sapphire and

its brilliance rivals that of a diamond. Cambodia's zircon deserves more respect

than it gets in world jewelry markets - the problem is that it is not well-known.

One problem is a lack of name recognition, or even misrecognition'. Many people hear

zircon and think zirconium, or cubic zirconium, a diamond simulant, a lab-grown,

synthetic gem, the stuff of late night home shopping networks.

Few people are aware that zircon is a natural gem and that it comes in colors that

vary from colorless to yellow-orange, and gold to a variety of blue hues - near pastel

to deeply saturated.

Almost all stones sold are flawless to the eye and to a 10X loupe (or should be).

But that is a problem too, since most of us know that if a stone is "too perfect"

it is probably not real.

Zircon's natural dispersion may also work against it. It can be nearly as brilliant

as a diamond, and if you have never seen a good zircon before, its deep-saturated

blue color and diamond-like flashing highlights might lead you to conclude it must

be fake. But they are real; stunning, flawless stones are being mined, treated and

cut in Cambodia every day.

Baw Gaew district is the oldest and most famous source of zircon in Ratanakkiri,

the only province where the stone is mined. Many Cambodians don't recognize the name

zircon, but it is widely known as t'bong baw gaew after the best-known source, or

t'bong khieu Ratanakkiri (blue Ratanakkiri gems).

In the last three years mining efforts have shifted to an area in the province called

Jomrum Bai Srok, which residents say was a refugee collection point and camp in the

early nineties.

All digging in Ratanakkiri is done by hand, with narrow shafts sunk into the ground

in gem-producing areas in search of layers of gem-bearing soil. Miners in one part

of Bai Srok dig to 15 meters and generally encounter gem soil at between ten and

13 meters. The stones are not embedded in rock, but lie scattered in loose, crumbly,

clay soil from which they are easily separated.

Hundreds of shafts have been sunk in and around Baw Gaew. The small town has grown

so much that temporary structures have been built over older working holes. Some

residents even mine underneath their houses.

Outside town a large, low hill is covered with holes, more of which are abandoned

than worked. The newest holes are clean of all vegetation, but abandoned holes can

be overgrown, so care is needed when on site.

Each working hole has a small windlass that allows a bucket to be dropped into the

hole. Miners climb down into the mine using hand and footholds cut into opposite

sides of the shaft.

Once a gem-bearing layer is found, it is scraped out. Then the bottom of the shaft

is expanded sideways, sometimes with dangerous results. Other shafts can be sunk

in line with the located gem-bearing vein in order to tap into it from a different


It is easy to spot the holes that are successful. If none or only a few stones are

found but the miners are still hopeful, the dirt is sorted out by hand by mud-slimed

miners sitting on the ground.

Successful shafts generate enough money to pay for water to pan the dirt. Miners

stand in small reservoirs lined with large plastic sheets and slowly sort out the

stones by swirling the soil in flat, tightly-woven baskets.

Miners say only 20 percent of the stones that they find are salable. No one would

say how much the rough stones sell for, but the on-site buyers are easy to pick out.

They are all clean, smartly dressed young men who carry small, powerful lights to

"candle" the stones.

Large stones can be rejected if they have too many cracks inside. A cut stone with

eye-visible breaks, fractures or inclusions has little value because almost perfectly

clear stones are quite plentiful.

In Ban Lung rough zircon is sold by the kilogram (5,000 carats) for $2-3,000 depending

on the average size of the stones. The customers are mainly Thai buyers who take

them back to Chantaburi to be treated, cut and sold at the famous gem markets.

Ironically in the recent past the most common name for zircon among jewelry buyers

in Phnom Penh was t'bong Thai (Thai gems).

Siew Chheng, a jewelry seller at the Russian Market, says the demand for zircon among

foreigners has increased over the past year.

Gem cutters in Ban Lung say that the largest cut gem they know of was about 40 carats.

A top quality stone of that size would cost about $50 per carat in Ban Lung (more

in Phnom Penh). Prices for top quality zircon can vary from $10 to $30 dollars a

carat, depending on the size of the stone.

I met a Tampuan miner who lived in one of four villages with small scale mining operations.

He had a 100 carat rough stone that he wanted to sell for 2.5 million riel (about

$640). Since he saw me as a potential buyer, that is likely to be substantially higher

than a negotiated price.

Ban Lung gem dealer Map says he uses five separate quality categories for cut blue

stones and three for yellow. Prices vary according to total carat weight and color

saturation, which comes from heat treatment.

Up from the depths of the earth, a miner squints against the light.

The heating process is only well enough understood and well enough controlled so

that statistical results can be achieved. You cannot predict what will happen to

a stone, but if it is done well, the change should be permanent.

Twenty percent of heated stones will turn yellow or white, while the rest will become

the more valuable blue. Only a small fraction of those will achieve the most valuable

highly saturated color.

Even if the 100 carat stone turns a deeply saturated, permanent, and therefore valuable

blue, one can expect to lose up to 60 percent of the rough weight when it is cut.

Finally, there is always the possibility that cutting will reveal breaks which were

not previously visible. That again reduces the size of the final stone or forces

the cutter to fashion several smaller stones rather than a large one.

The greater the number of stones cut, the more of the original weight will be lost.

And the smaller the average weight of the stones, the lower the per carat price.

There are artificial zircon stones around, but if you buy from any of several jewelers

with established reputations for integrity in Phnom Penh, you will have a stone you

will enjoy for many years to come.

Traveling to Baw Gaew

Reaching Baw Gaew from Ban Lung town is never easy, and worse still in the wet season.

One way is to get a Chinese-style jeep, four of which wait in front of the town's

taxi stand at the main market and leave when full.

Motorcycle taxis are also available for 10,000 riel one way, but they use paths rather

than the main road for two-thirds of the journey. The route is more scenic, but the

last ten kilometers takes you down slippery hills and jungle.

There is simple accommodation and safe food and water available at the mining town.

Reaching there on your own is not recommended.

John C. Brown has studied gem identification and grading at the Gemological Institute

of America. He visited Ban Lung and Bai Srok July 13 - 19.

Email: [email protected]


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