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Australian White Opal

Written by Modern Jeweler On May 2, 2013.

Opal was highly valued in Ancient Rome. But the gems they treasured wouldn’t rate a second glance today. The opal of the ancient world was a cloudy white gem with a few subtle pin pricks of play of color. This opal was mined in what is now the Czech Republic, near Czerwenitza.

Since the discovery of Australia’s incredible opal deposits in the nineteenth century, the standard for beauty in opal has been redefined. Australia’s opals have more fire, more transparency, and more abundance than the ancients dreamed possible. Thanks to the richness of Australia’s deposits, white opal has become a staple in affordable fine jewelry. The average consumer can own an opal that would put the opals of emperors to shame.

Pretty For Pennies

Mass merchandisers have found opal an ideal choice for affordable jewelry, especially earrings and pendants. For extremely little money, white opal provides a beautiful gem, that is unique, thanks to its individual pattern of play of color. According to a New York dealer, the most popular types of white opal in the mass market are: 1) milky white with pale multi-colored pinfire, or 2) blue green with broad flashes of color.

Because a large amount of low-end opal is used in earrings, pinfire is more popular than broad flash: it’s easier to match pairs.

Up The Ladder

Consumers who pride themselves on wearing quality will probably not be happy with largely opaque, pale, no-color-play opal- no matter how cheap. This opal hardly lives up to its name, derived, in part, from the Greek word opallios, which means “to see a color change.” But to get stones with an interesting array of color, plus some translucency, expect to pay a lot more than is asked for run-of-the-mill anemic opal. Stones that boast strong foreground reds, greens and blues are definitely not available at trinket prices.

The next step up is what dealers call “crystal opal.” This term refers to the look and not the structure of stones. These opals sport, in one dealer’s words, “a translucent glass-like appearance with full colors seemingly suspended in a transparent base.”

But “crystal opal” is only one of the varieties of better opal. The finest usually show no identifiable background color, just a continuous, unbroken array of vivid color patches or patterns. These stones will cost about the same as better aquamarine or imperial topaz.

Although commercial-grade opal is largely what jewelry manufacturers use these days, there seem to be strong stirrings of collector interest in better opal.

Improving the Odds

Opal has a weakness: some stones eventually crack because of structural weaknesses made vulnerable by heat and dehydration. But the problem can be minimized by dealer quality control.

First, the knowledgeable dealer knows which locations in Australia produce the most stable opal (Andamooka is famous for such stones), and shops accordingly. As an extra safeguard, most dealers hold all polished stones for several weeks and return any that crack.

Second, because those opals that crack tend to do so sooner rather than later, the responsible dealer will refrain from selling newly purchased or polished stones for a certain period of time to let nature weed out any losers. Dealers we interviewed call this procedure “curing” and subject both rough and cut stones to it.
Unfortunately, the dealer’s ounce of prevention can be undone by abuse in display cases.

Since those opals with a high water content are the most prone to cracking (also called “crazing”), prolonged exposure to bright lights in a closed, unventilated showcase is an invitation to trouble. Thankfully, cracks are often skin deep and can be buffed out on a polisher’s wheel.

Australian Sapphire

Written by Modern Jeweler On May 2, 2013.

Connoisseurs may glorify rare Kashmir sapphire with its soft velvety blue. Collectors may extol the hard-to-find Burma breed with its crisp royal color. And specialists in swank gems may laud the Sri Lankan variety for its cool stately hues.

But few sing the praises of Australian sapphire, even though it was about the only variety known to the common man for nearly 30 years until Thai sapphire, and later African, supplanted it as a market mainstay. Now it is unlikely anyone ever will.

For Australia’s claim to fame was in the realm of quantity, not quality. Indeed, it was to bulk what Kashmir was to beauty. Since the early 1960s, it had enjoyed unrivaled leadership as a sapphire producer. Then between 1985 and 1991, it went from supplying 70 percent of the world’s sapphire to less than 20 percent. That killed Australia’s reputation as the key source of bread-and-butter stones. Even when it was, dealers disliked its dark-toned, slightly greenish-colored goods.

Strangely, the consistent inkiness of color disparaged by connoisseurs made this sapphire indispensable to mass manufacturers and merchandisers. As late as 1989, dealers assumed that any mass-produced piece of sapphire jewelry used Australian material because it was the only reliable source of matchable blue tones.

Because America was the world’s chief manufacturing center for mass-production jewelry, the vast majority of Australia’s blue sapphires wound up here. But as chain stores became a bigger factor in Europe and as new markets for low-end jewelry emerged in the Pacific Rim area, exploding demand for inexpensive sapphire suited to mass production drove up prices for all but the lowest-grade Australian goods at least 50 percent in just two years.

Spiraling prices prompted exploration for sapphire in Thailand, long a producer of the gem. And since the Thais bought and cut 90 percent of Australia’s production, success with mining at home was sure to hurt sales in Australia. Matters weren’t helped by the fact that Australian sapphire resisted oven touch ups.

Heat Treat

Ever since meaningful sapphire production began in Australia around 1890, bringing these gems to market has always been handled by people as strongly versed in gem enhancement as they are in cutting.

Dealers from Idar-Oberstein, Germany’s centuries-old cutting center, were the first market-makers for Australian sapphire. They bought the lion’s share of rough found at the Anakie alluvial fields in central Queensland (Australia’s most significant deposit until 1959 when large-scale mechanized mining began at the New England fields of northern New South Wales), processed it back home, then sold the finished goods to Czarist Russia. World War I and the Russian Revolution of 1917 ended Australian sapphire’s initial period of popularity.

Part of that processing may very well have included some form of heat treatment. How else could the Germans have succeeded with Australian sapphire given the gem trade’s then somewhat low esteem for this material. In 1908, gemologist Max Bauer wrote rather unflatteringly that “Australian sapphires, as a rule, are too dark to be of much value as gems.” Very likely the Germans were quietly broadening the new sapphire’s appeal the way they had broadened the appeal of Brazilian aquamarine-namely, by heat-treating stones to improve color.

Certainly, oven alchemy is the key to Australian sapphire’s second and far greater wave of popularity in our time. Using heat to lighten up the dark color, dealers from Thailand, the main buyers of Australian sapphire from 1960 on, were able to create a market for what otherwise would have been low quality rough. For more than 20 years, about 10 firms were buying an estimated 90 percent of the output from Australia’s fields.

Heat dissolves the heavy silk that is a major internal characteristic of Australian sapphire. Unless this silk is removed, Australian sapphires tend to be plagued by pronounced blue/greenish-blue dichroism (transmission of two different colors when a gem is viewed in different directions) that imparts an objectionable greenish cast to stones. From the look of recent purportedly Australian sapphires we’ve seen, the heat treaters of Bangkok have become quite expert at minimizing annoying green.

As the market for Australian blue sapphire has declined over the last decade, miners have started to look at yellow and green sapphires from these deposits. It’s ironic: sapphires that were originally dubbed unmarketable for the yellow and green colors, as overtones to their blue, may eventually become celebrated for those colors themselves.

Australian Black Opal

Written by Modern Jeweler On May 2, 2013.

O, the power of the pen. With just one strange plot twist in his 1829 bestseller, “Anne of Geierstein,” Sir Walter Scott destroyed the European opal market for nearly 50 years. And he did it just by having a character falsely accused of being a demoness die shortly after a chance drop of holy water fell on her opal and quenched its mysterious, fiery color. Convinced Scott was warning them that wearing opal could bring bad luck, suggestible readers stopped buying the gem. Within a matter of months, the opal market had crashed and prices were down more than 50 percent.

It took a remarkable find of black opal at Lightning Ridge in New South Wales, Australia, in 1877, to revive the market for this gem. Australia’s spectacular new opals took the world by storm. Indeed, there have been almost no opals found in the last 50 years to match what came from Lightning Ridge in its late nineteenth and early twentieth century heyday. No wonder dealers sometimes liken Lightning Ridge’s impact and significance to that of Kashmir for sapphire, a Himalayan source discovered around the same time, that set the standard for sapphire in the same way Lightning Ridge did for opal.

Lightning Strikes Once

Black opal is far rarer than white opal. In fact, there are only two active black opal localities in the world, both in Australia. Of the two, the older, Lightning Ridge, is said to be the only one to produce true black opal. The other, Mintabe, is known more for gray-to-grayish-black material. Some purists even protest calling Mintabe stones black opal. They do so on both geological and aesthetic grounds.

Traditionally, black opal was considered a variety of opal found in rock formations called nodules (or “nobbies” in the trade) as opposed to white opal, which is found in seams. But when Mintabe, whose opal is also found in seams, was discovered, this geology-based distinction began to blur- at least among dealers.

One can see why opal dealers insist that Mintabe’s dark- gray material be accorded full standing as black opal. If they had to restrict their definition to goods from fast-depleting Lightning Ridge, the future of this gem would be in grave doubt. For even when production from Lightning Ridge and Mintabe are pooled together, there is still far less black than white opal. Given its relative scarcity, black opal has never lent itself to volume jewelry use the way white opal has. As a result, black opal remains primarily a special order stone in this country. But the few who buy it here generally look for the same things the Japanese do: base color, hue mixture and color pattern.

Basics of Opal Beauty

When dealers evaluate black opal, they start with its base color. The darker the base- or what dealers call “potch”- of an opal, the more pronounced and vivid its color. That’s because an opal’s beauty is the product of the contrast between its color play and its background.

As for ideal color in black opal, most experts look for the predominance of red and then orange. “Stones that appear all or almost all red are the most coveted,” one dealer explains. “Increasing amounts of blue and green will reduce their value.”

But specific color isn’t all that connoisseurs want in a fine black opal. The pattern that they take is equally important. For years, the most prized pattern was what dealers call the “harlequin”: well-defined squares, rectangles, triangles or diamonds of color in both symmetrical and asymmetrical designs.

Today, unfortunately, the harlequin pattern is encountered only in older pieces. No new stones with this pattern have been mined in years. Failing to find stones with big blocks or even chunks of color, connoisseurs must content themselves instead with swirls. Often you’ll hear them describe the best patterns that can be hoped for in black opal today as stones that exhibit broad well-defined flashes of color (called “rolling flash” in the trade) that change kaleidoscopically as stones are turned in the hand. Yet even these patterns are far from plentiful.

Realistically, the top black opals that consumers are likely to be offered nowadays feature color patterns comprised, at their best, of lively pointillistic dots. As these dots get smaller and less vivid, they come to resemble what the trade calls “pin fire.” Such black opals are the most commonly found and least expensive.

Arizona Peridot

Written by Modern Jeweler On May 2, 2013.

Options for second careers are few in Globe, Arizona, a desert town 90 miles east of Phoenix. So why not open a takeout place or pizza parlor? Globe has only 5,000 residents, that’s why. How about a tourist shop? Nah, the San Carlos Apache Indian reservation, 20 miles east of Globe, grabs most visitors.

Luckily for Tyree Trobaugh, a miner who retired in 1971 at age 65, the reservation is the site of the world’s largest peridot deposit, producing, says the U.S. Bureau of Mines, at 80 percent of all current supply. What’s more, the Apaches, to whom the U.S. government awarded mineral rights decades ago, prefer to sell the rough that they alone are allowed to dig to a small number of nearby dealers, most based in Globe.

Trobaugh has been one of this handful for the past 20 years. Nevertheless, the decision to become a peridot specialist has seemed a particularly sound one of late now that the gem, the birthstone of August, is now fashionable.

As a result, Trobaugh finds himself buying, on average, hundreds of pounds a week of freshly mined material from about 100 different Native Americans. “They come with anywhere from 1 to 500 pounds of peridot, mostly small in size, and applied in everything from cereal bowls to buckets.” He says.

Peridot doesn’t make millionaires of those who mine it. To the contrary, Trobaugh estimates that total yearly production probably don’t exceed $250,000.

At around $7 to $8 per pound, peridot rough must be found in large lots for mining to pay off. The hundreds of people engaged in digging for the gem, often in family teams, gather as much of it has they can in a short period, then dispose of it.

But at least it’s a job in a region with few employment options. And with peridot gaining swiftly in popularity, demand is likely to make mining it a job for more and more Apaches.

Light and Lively

While not yet a staple like blue topaz or amethyst, peridot has reached the lower rungs of vogue status. This status makes sense at a time when clothing designers are making heavy use of light, vibrant yellow-green.

Ironically, there was a time when the jolly lifesaver-green of Arizona peridot was looked upon with disdain. Proper peridots were supposed to exhibit the graver green of the Burmese and Egyptian varieties. Connoisseurs and purists still consider stones from Burma’s Mogok tract, Egypt’s Zabargad Island, and Pakistan the best of the breed. But a new generation reared on American peridot (supplies from Burma and Egypt are a trickle) has taken to its light and lively color.

What’s more, this taste is more than mere accommodation to the fact that Burma and Egypt are largely has-beens among gem producers. For one thing, most of the new generation of gem dealers, jewelry designers and retailers have little or no familiarity with Burmese peridot. For them, Arizona defines the range of color possibilities for this gem. The choice is between China and Arizona, with Arizona stones generally producing a more attractive green.

Those possibilities are completely different from those for Burmese and Egyptian stones. While Arizona peridot, like all other deposits of this olivine, is found encased in or extruding from volcanic rocks such as basalt, geological circumstances different from those in Mogok and Zagarbad allowed formation of typically smaller crystals.

As a result, the average size for polished Arizona peridot is one carat or less. Stones up to four carats are common, but from there to 12 carats they are rare, 12 to 20 carats very rare and above 20 carats almost impossible to find. On the other hand, you frequently see large Burmese and Pakistan peridots.

Clean Green

Given the preponderance of sub-carat peridots, the gem is most often used as an accent stone or part of a combination of small stones. In sizes below a carat, peridot is certainly one of the most affordable green gems. But because availability drops off sharply above four carats, prices take a jump for fine stones that are larger.

That is, provided they’re clean and crystalline-not included or fuzzy. Peridots from different localities have their own signature inclusions, some fluid, some solid. (Burmese peridot, for instance, is plagued by tiny flakes of biotite which cutters call “rain.”) Arizona crystals are usually so heavily included that even when sizable, large stones are impossible to cut clean.

Andesine Feldspar

Written by Modern Jeweler On May 2, 2013.

Editor’s note: Andesine feldspar is currently the subject of several lawsuits. For more updated information on this gem, check our Gem Profile on Oregon sunstone. The following is the original text from our March 2006 Gem Profile, which was written when the attractive and mysterious material was first appearing on the market.)

ANDESINE: Red-Hot Feldspar

You’ve got to hand it to Jewelry Television, the 24/7 gemstone shopping network based in Knoxville, Tennessee, that has positioned itself as a gemological Discovery Channel. The station knows good things when it sees them. And when, as is often the case, it’s the first to lay eyes on an affordable new gem, it lays enough cash on the table to make sure no one else will see it until it has built a thriving market. With a viewer base of 65 million people, the network often needs months to satisfy large audience appetites.

Nevertheless, Jewelry Television doesn’t blindly lunge into new stones. Because it takes so many risks, it must temper need with caution, giving each newcomer several screen tests to see if it will merit voracious stocking. Of all the gems the network has premiered, none has risen to quicker popularity than andesine, a red plagioclase feldspar whose origins remain a closely guarded-or deliberately muddled-secret. At first rumored but never confirmed to be from the Congo, the current source is most likely western China, possibly neighboring Mongolia or Tibet.

From a marketing standpoint, andesine has all the traits of a Chinese-origin or Chinese-controlled gem. That usually translates into a sell-now, sell-all-you-can philosophy. Since Tucson 2004, supplies of red (as well as green) feldspar have been near ceaseless, something which has worked to Jewelry Television’s advantage ever since it first took a chance on the gem when introduced to it at the show.

Chinese dealers priced their andesine to move from the start. But once this feldspar proved a winner, Jewelry Television bought it in price-pummeling bulk. Last month at Tucson 2006, the network purchased tens of thousands of carats just from two suppliers-and put in open-ended orders for future production when and if it materializes. “Demand is staying way ahead of supply on this one,” says buyer Jay Boyle.

No wonder the station charges $80 to $200 per carat-depending on color, clarity, and size-for the four hues of andesine it offers: red, orange-red, orange, and honey-red. While some exceptional stones fetch more, even their several hundred dollar-per-carat prices reflect the network’s immense checkbook leverage. What makes andesine so telegenic? At its best, this gem boasts a rich red that invites show hosts to compare it to ruby. Is this an exaggeration? “With a below-average return rate for andesine, shoppers are obviously happy with what they receive,” says gem buyer Shawn O”Sullivan.

Incredibly, more than 90 percent of the andesine Jewelry Television sells is loose, which suggests that most buyers are collectors-or, perhaps, still pondering ultimate use. Since network customers tend to be versed in the gems they buy, they probably know andesine has a hardness of 6 to 6-1/2, which should deter mounting in rings. But so does tanzanite and that’s been finger fare for nearly two decades.

As andesine’s red glare spreads off screen to jewelry stores, the gem is coming under intensive gemological scrutiny. Like garnet, feldspar is a large, sprawling family and classification has been tricky, if not controversial. So before putting the stone on air, Jewelry Television asked GIA for nomenclature guidance which it is now following-until or unless the institute changes its thinking.

IDENTITY PROBLEMS

Before andesine appeared, the best red feldspar available was medium-toned, orangey material from Oregon known as sunstone because of its shimmering reflections called aventurescence (schiller) from tiny crystals clustered inside. Sunstone, which is a market rather than a mineralogical name, belongs to the oligoclase branch of the feldspar family-a family that needs genealogy charts to figure out precise memberships in it.

Apparently, andesine is an intermediate member between oligoclase and labradorite, just on the borderline with the latter. Such overlapping chemistry tempts merger names such as “andorite” and “labrasine.”

Overall, family placement in the six member (albite, oligoclase, andesine, labradorite, bytownite, and anorthite) plagioclase group depends on several factors, including refractive index (around 1.55) and shifting ratios of albite to anorthite (the flanking members of this group).

One thing for sure, andesine is not sunstone because it lacks schiller and is usually far deeper in color. However, we’re not too excited about calling it red labradorite either. To us, that’s like calling pink or even golden sapphire by the name of ruby, especially since only a small percentage of andesine is real red in the sense that sapphire is true blue. What’s more, andesine also occurs in green that exhibits other colors such as red in alexandrite-fashion under different lighting conditions.

Here we come to one of the most curious elements in the andesine success story. Red andesine is the first feldspar I can think of that is appreciated for pure monochromatic color the way, say, spinel is.

It is green andesine that is more characteristic of feldspar because it lives up to traditional expectations of color play and other special effects for this gem group. Remember that moonstone and rainbow labradorite are among the most famous feldspars-and both are celebrated primarily for their blend of color and appearance. On the other hand, red andesine finally puts feldspar in a color class with red corundum to which its very likable best stones are justly likened.


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