GemNotes

The ’60/60’ Diamond Certificate

High-tech advancements such as the Gemological Visualization System from Diamond Technologies in Georgia, the Fire-Scope in Japan and the Sarin in Israel can measure every angle, percentage and millimeter of a diamond. Some even claim to measure symmetry, brilliance and dispersion. Yet the industry still can’t agree just which proportions, brilliance, dispersion reading or angles give diamond its greatest beauty.

Many swear by Tolkowsky’s original proportions. Yet how many retail jewelers or diamond manufacturers actually carry diamonds with 53% tables? (Remember that Tolkowsky did not give a range for table size, nor did he include any girdle thickness measurement.) And new studies of brilliance, dispersion and symmetry question even Tolkowsky’s numbers.

Despite all this high-tech analysis aimed at finding the perfect proportions, many diamond wholesalers now promote something called the 60/60, meaning a diamond with a 60% table and 60% total depth – plus, hopefully, very good polish and symmetry and no fluorescence. This has little to do with perfection or beauty, but a lot to do with how easy it is to sell a certificate rather than a diamond. Diamonds with such certificates are easy to sell because they require little explaining to the retailer and command a profitable price.

It’s true that a 60% table is easy to understand. We all know this means that the top facet is 60% of the crown or width of the stone, giving good flash without crowding the top. But total depth is the sum of three measurements – crown height, girdle and pavilion depth, each figured as a percentage of the total width – and all three can vary. Do the crown facets create dispersion? Dispersion improves as crown angles approach 341/2°. Is the girdle too thick or thin? Is the pavilion too deep or shallow? A 60% total depth actually means very little without knowing the other details.

A 60/60 reading could mean a 31° crown angle with a 12% crown height, a thin girdle (2%) and a 46% pavilion depth. Such a diamond probably looks somewhat lifeless; its shallow crown angles mean less dispersion, while a fairly deep pavilion means less brilliance. A 60/60 reading also could mean a 37° crown angle with a 15% crown height, very thick girdle (5%-6% for a 1-ct. diameter) and a 39%-40% pavilion. Such a stone might be somewhat more dispersive, but have much less brilliance and a somewhat watery look because of its very shallow pavilion.

What about “very good” polish and symmetry? It’s a myth that these always improve the appearance of a diamond. Since they have no effect on crown angles, pavilion depth, etc., a diamond could be graded “excellent” on each and still not be very pretty. Indeed, very good polish and symmetry can actually intensify the poor look of a badly cut diamond. But when its proportions make a diamond look brighter, very good polish and symmetry will magnify that brightness. Proportions determine whether light is returned and whether some of that light is broken into spectral colors; polish and symmetry do not.

Finally, what about fluorescence? It used to be that faint or medium blue fluorescence was said to enhance a stone’s color in daylight. So why do dealers want “none” listed on a report? Because it requires no explanation, making it easier to sell.

Some diamond grading reports include information about crown angles, pavilion depth and dispersion, as well as brilliance. But the GIA Gem Trade Lab grading report, which lacks such additional information, still commands the highest regard for accuracy. Wholesalers use GIA/GTL reports to sell diamonds, knowing that many probably would not command as high a price if GIA were to include more information.

What all this means is that you still must look at each individual diamond to see its beauty. And you still must wait for new technology to figure out what really is “ideal.”

AGS Members Query Outside Use of Lab

The American Gem Society laboratory has been open to non-AGS jewelers since September 1996, and not everyone’s happy about that. “In a word,” says one, “it stinks.” Now competitors have access to the AGS cut grade, which some members considered proprietary. “How can we compete against the guy across the street if they can use our cut grade and our laboratory?” they ask.

Trouble began almost a decade ago, as AGS struggled to maintain and even build membership. To provide a perk, AGS asked GIA’s Gem Trade Lab to offer diamond grading reports with an AGS cut grade to AGS members only. (AGS jewelers have promoted “ideal make” since the group began back in 1934.) When GIA refused, AGS decided to create its own members-only diamond grading laboratory. This would allow AGS jewelers to offer something no other jeweler could: a certificate from an “independent” laboratory with an AGS cut grade.

Initially, grading was to be restricted to members. Only after about three years, once the lab was well established, was it to be opened up to the entire trade. But Bill Underwood, a Fayetteville, Ark., retailer and chairman of the lab’s board of managers, says there just wasn’t enough usage by AGS members. “We contacted the entire AGS membership” to plead for more support, he says. The response was insignificant. To stay in operation, the lab needed more business.

Underwood stresses that if “there are any abuses of our grading reports by non-AGS members, we will take action against them and then we may have to look at our decision again.” Indeed, there already have been abuses. One non-AGS store, for example, decided to use the AGS logo in an advertisement, simply because it carried diamonds with AGS certificates. This suggested that the jeweler was somehow affiliated with AGS, so AGS had the logo removed from the ad.

“We have good feelings about the lab,” says Underwood. “We’re headed in the right direction.” That direction involves making the lab more consumer-oriented than any other. Some labs offer a grading service, he says, but aren’t concerned with what happens to their report after the fact. “Our #1 goal,” says Underwood, “is that whatever we do, we do it in the best interest of the consumer.”

Still, the decision to allow outsiders to use the lab disappoints some AGS retailers. “It’s just one more thing that dilutes the value of my membership,” says one. “If we don’t have the support [from AGS members], why have a lab?”

Emeralds found in Paraiso, Brazil

George Williams, brother of Bear Williams of Bear Essentials, a jewelry and colored stone wholesaler in Jefferson City, Mo., recently announced discovery of a new emerald deposit in northern Brazil. This new find in Tocantins – a state north of Goias, which also is known for small emerald deposits – is situated some 20 kilometers from the town of Paraiso, population 30,000. A local farmer literally stumbled upon the deposit; he and his relatives pulled material right off the surface until word spread. Now co-ops and individual miners have moved in.

The emeralds are decent. Better material is of medium tone, moderately strong saturation, very slightly yellowish green. Much of it contains blocky two-phase and thin needle-like inclusions. It remains to be seen if there is enough material with dense enough needles to produce any substantial quantity of emerald cat’s-eyes.

George Williams has lived in the area for two years. He’s seen garimpeiros (gem prospectors) flood into areas like this before and expects bickering over leases to occur. Generally, federal police will come in to help settle the squabbles, then the mining commission will organize the area. That’s when larger mining concerns show up.

The emerald ore body is about 2.5 kilometers long and 250 meters wide, descending at a 24° angle. The first 50,000 square meters, where the ore breaks the surface, has been allocated to the garimpeiros. So far, they haven’t mined much deeper than 3 meters.

I had an opportunity to examine two rather nice emeralds from the deposit. A 1.91-ct. emerald cut was insured at $800 a ct.; a 1.52-ct. oval was insured for $1,500 a ct. Since they were moderately included, yet still very transparent and relatively clean to the eye (SI in clarity), I was not surprised to find both fracture filled with a foreign substance. Both were well cut with good to very good polish and symmetry. The emeralds are being marketed by Bear Essentials.

Opticon & Hardener vs. Cedarwood Oil

In a recent letter to friends, respected emerald supplier Ron Ringsrud of Constellation Gems, San Francisco, compares the fantastic results claimed for certain emerald treatments to the exaggerated claims for plastic surgery, liposuction and the like. Sure, fracture filling emeralds does improve their appearance and mask many visible breaks, but it isn’t a magic elixir. At least not yet.

Ringsrud is a strong supporter of cedarwood oil, or cedarwood mixed with canada balsam. He likes the refractive index of the Groom/Gematrat product (see JCK, September 1997, page 80), but claims that it is too thick to be completely effective. To fill very thin fractures in emerald, you need something less viscous, like cedarwood oil, he says.

Although most jewelers would accept cedarwood oil, the epoxy resin Opticon is becoming the filler of choice for many emerald merchants. But Opticon with hardener is getting some very bad press.

The RI of Opticon and other recent treatments may be closer to emerald than oils, making them much more difficult to detect. Using a separate hardener to seal the Opticon filling inside the fracture makes it even more difficult. Is this good or bad? Masking fractures obviously is the purpose of fillings. Is the trade saying that fillings are OK unless they do their job of making fractures invisible too well?

A reputable emerald wholesaler in the U.S. says many in Colombia and Brazil choose Opticon because it costs only pennies. Even if a gem dealer requests cedarwood oil and is willing to pay the extra required, there’s no guarantee that he’ll get it. “They could charge you for cedarwood, fill the emerald with Opticon and make even more money.”

Fracture filling will become even harder to identify as treatments become more sophisticated. That’s why jewelers need to find ways to educate their sales staffs. GIA has started a year-long study into all emerald fillings – oils, resins and others – to determine the durability and effectiveness of each. This should put to rest all the unsubstantiated claims which Ringsrud is quick to dispute.

Neary Resources Tests for Red Beryl

The Wah Wah mountains of Utah are again being tested for possible commercial production of red beryl. According to Huitt Tracy, spokesperson for Neary Resources of Canada, test results show significant finds, 566 cts. per ton.

Red beryl (sometimes facetiously referred to as“red emerald”) was popular amongst collectors over a decade ago when only small amounts and small specimens were uncovered. Since then, a synthetic red beryl has made its way into the market. Until natural material is commercially available and demand for it builds, there will be little market for a synthetic.

Munsell Correlated to GemDialogue

Howard Rubin has offered the GemDialogue system for color grading colored gems and diamonds for more than 25 years. It is very accurate and repeatable but, until now, didn’t relate to any international color standard.

Munsell, based on CIE color notations, is probably the most familiar color system. Its master set of two-dimensional paint chips is arranged on hue pages which vary in tone and saturation. GIA’s Gemset uses three-dimensional gem-cut plastics mounted in a Munsell-style hue page with variations of tone and saturation. The advantage of this system is being able to compare gemstones to three-dimensional transparent color masters. GQI’s “The World of Color” uses Munsell chips to show saturation and hue variations on a single-tone page. Colorscan (developed by the American Gem Laboratory) and GemDialogue, the other color systems used by jewelers, were not related to Munsell. This meant that jewelers and gemologists using other grading systems could not relate them to GemDialogue or Colorscan descriptions.

Rubin and partner Gail Levine spent two years physically matching colors from each of the color systems mentioned here. They’ve produced a book, called GemDialogue Tool Box, which compares each system to the other. Now someone can relate Gemset color grades to Munsell, and Colorscan’s grades to GemDialogue’s. Each system gets its own section, explaining terminology used and listing each designation with a comparable GemDialogue notation.

China’s Emerging Akoya Markets

A saltwater cultured pearl market is emerging in Southern China, from the peninsula in southern Guandong Province to Hong Kong. Some 2,000 to 3,000 small, privately-owned akoya farms now operate in China.

The industry, still struggling financially, has received little support from the government, so quality has been lackluster. The Chinese akoya pearl havest totaled roughly 20 tons (about 19.9 million grams) in 1996. Gem quality can be achieved, but it’s rare; pearls rated even “good” make up only 5% of each harvest, with medium, or marketable, quality about 60% of the hama-age. (This is the raw material gathered from a pearl harvest, before processing).

Although Japanese and Chinese akoya oysters supposedly have the same ancestor, the interior lusters of their shells differ noticeably, which affects pearl color and orient. There are other differences, too. A drop in temperature crystallizes nacre and gives Japanese pearls a last-minute luster before their December harvest; water temperatures in Chinese cultivation areas are higher. Many Chinese akoya pearls have a “flat spot” on one side because of cheap nuclei cut from the dropped edge of shells.

However, Chinese processing techniques are equal to those in Japan, and cultivation techniques are improving, says Thomas Chan. He’s president of Cheergem Ltd., a Hong Kong-based company with factories in China.

Cheergem is investing in the industry and overseeing quality efforts at the cultivation farms. Chan has committed to educating cultivators. He sets up classes to teach techniques, including the importance of a one-year cultivation period (proper, he says, in China’s warmer waters). When cultivators receive a certificate for these classes, they become eligible for a contract with Cheergem, which processes 15,000 akoya pearl strands per month at its factory in Zhanjiang, China.

The industry has come a long way since the early ’90s, when a university professor first cultured pearls on a small-scale based on Japanese research. In 1992, a Japanese visitor bought some hama-age, took it back to Japan for processing and began publicizing Chinese akoyas at trade fairs. Groups of Japanese dealers visited China to learn more, and cultivators began spreading the word that pearl farming was a hot prospect.

“First the farmers were growing vegetables and chickens, then they started growing pearls and sharing technical information,” says Chan. “At first the idea was simply quantity, and we ended up with a lot of half-baked pearls.”

Financial problems. Around the time this new industry was emerging, Chinese leader Deng Xiaoping began enforcing a “hands-off” policy to encourage private industry. Because of this government reluctance to get involved, says Chan, the new akoya pearl industry didn’t receive the financial support or services, such as export inspection, it needed to get off the ground.

Companies began investing in China’s akoya pearl industry, but few stuck around after the initial boom of 1994 and 1995, when more than half of the factories in Zhanjiang closed. Cultivators, who had sunk all of their money in pearl farming, began to need food for their families and cashed in their crops – sometimes only three months after the nucleus had been inserted into the oyster.

“At first, farmers borrowed from banks, but when they got the money, many would spend it immediately because they’d never seen that kind of money before,” says Chan. “Banks stopped lending to pearl farmers.”

Chan believes that private investment is the only way to help the industry grow in the right direction. Now that the akoya industry looks like it’s here to stay, the Chinese government is taking an interest. “Unfortunately, the government wants production to increase like freshwaters,” Chan says. “They want it to double every year. They only care about the figures.”

But Cheergem will continue to preach the gospel so popular with its Japanese counterparts: better quality. Chan dreams of starting a quality standards system to register farmers by city, county and village and require licenses for technicians and nucleus dealers. He is setting up recreation stations to teach the theme of quality.

“We have to pass the message to farmers that growing a pearl is like having a baby,” he says. “You have to keep it healthy, and you can’t take it out before the time is up.”

Russia, China Plan to cooperate

Russia and China have agreed to cooperate in exploring and extracting diamonds, delivering rough and polished diamonds, and producing jewelry. A joint working group is being set up to implement the agreement, which follows the signing of a letter of intent in September by Gokhran, the Russian fund of precious metals and stones, and the Chinese Ministry of Geology.

Two joint ventures are to be set up in China to cut Russian diamonds, according to Alexander Shkadov. He is director of the Krystall factory in Smolensk, Russia’s biggest diamond cutting facility, and president of the Association of Russian Diamond Producers.

The Russians note that the agreement with China is in accord with the rough diamond distribution agreement signed in October between Almazy-Rossii-Sakha and De Beers.

Dead Loan Deal May Cut Production

The collapse of a half-billion-dollar loan deal between NatWest Markets and Russia’s diamond mining agency won’t have any immediate effect on diamond supplies. But that could change down the line.

NatWest Markets repesented several western banks which had been poised to lend $500 million to help Almazy-Rossii-Sakha – which mines and markets the majority of Russian diamonds – rebuild its deteriorating mining infrastructure. ARS badly needed the funds to finish construction of the Jubilee mine and develop or refurbish other diamond mining areas.

NatWest agreed to the loan package more than a year ago, but suspended it until ARS and Russia reached a formal agreement with De Beers. Although the De Beers agreement finally went through in late October, NatWest decided to renegotiate the terms of the loan. Neither side could agree on the unspecified changes.

Analysts do not believe the loan collapse will have any short-term impact because the majority of Russian production comes from Udachnya, which remains fully functional. However, production from that mine is expected to decline within a few years. ARS will be hard-pressed to make up the short fall if there are no funds to develop Jubilee or some newly-discovered pipes.

Simulated Daylight for Gems & Jewelry

Tailored Lighting Inc. of Rochester, N.Y., says it has met the challenges of lighting jewelry and gemstones (in a display case or an entire store) by inventing “simulated daylight,” a 50-watt bulb called the SoLux lamp. The bulb emits a color temperature of 4700° Kelvin. It’s 56% warmer than incandescent bulbs and lights items in a closer representation of daylight.

Lighting affects perceived color of gems and jewelry in many ways. Incandescent bulbs tend to emphasize the color yellow in diamonds, causing a detrimental yellowish tone, but they bring out the best in warmer-toned gems, such as rubies or pink tourmalines. Fluorescent lighting is preferred for emeralds because of the predominance of green in commercial bulbs. However, most professionals agree that a majority of gemstones are best displayed in the natural light of day, or 6400°K.

The inventor of the bulb is Kevin McGuire, Tailored Lighting’s president. He says SoLux’s patented new thin-film coatings and filaments help to create an effect more like daylight. The coatings act as filters that reflect indigo-violet-blue light, while the filament directs warmer tones, such as red and orange, through the back of the bulb. The bulb also emits fewer damaging ultraviolet rays and generates less heat, both of which are preferred by jewelry stores, galleries and museums. In fact, New York’s American Museum of Natural History is using SoLux bulbs in its “Nature of Diamond Exhibition,” which opened in December.

SoLux is receiving endorsements from jewelers. “I can tell you it’s fabulous lighting,” says William J. Scheer of Rochester, who uses the bulb in his jewelry showcases. “This light works well for both colored stones and diamonds … Somehow the stones look more real, and you don’t get that tremendous heat you get from other light sources.”

Peter Thibault, diamond buyer at Christian Bernard Jewelers, Secaucus, N.J., uses the bulbs in some of his diamond cases. “I like them better than standard halogens, though for us it means using more lighting fixtures than we used with other methods. It may not be a light for everyone because distance is a factor, and there is an optimum distance with which to use these lights … But obviously we are pleased with the color of the light; it makes it easier to show D and E quality stones because they do not look yellow as they might in conventional lighting.”

McGuire says that his company is developing 5000° K bulbs, as well as those with lower Kelvin equivalents, which should be available early this year. Tailored Lighting Inc., 1800 Lyell Ave., Rochester, NY 14606; (716) 647-3199, fax (716) 647-3203.

Birthstone report: Amethyst, the February Gem

Amethyst is one of the most common gems among birthstones. It is quartz and it’s purple. Supply is plentiful and prices are relatively low. So what else is there to say that might help you sell this gem? Plenty.

First, the color is not “just purple.” While it may seem to be one hue, there can be some secondary hues of red or violet – some of which create the most spectacular amethysts in the world. And even within such a limited hue, the variety of amethyst available for your inventory is amazing.

You can choose stones with increased or decreased saturation (from pale, near colorless to vivid or intense color). You can pick lighter or darker tones, add some yellow/orange citrine for contrast and even combine fashioning techniques such as carving or etching. Of course, there’s nothing wrong with stocking a few standard faceted pieces, along with some increasingly popular cabochons. All of these add variety to a perhaps seemingly boring birthstone.

Sources. Brazil produces most amethyst, although a good number come from Bolivia, Uruguay, Southern Africa (including South Africa, Namibia, Zambia and Zimbabwe) and the U.S. (Montana, North Carolina and other states). Once historically very important, Russia now yields only synthetic amethyst.

Ametrine combines amethyst and citrine in the same gem. Since its commercial arrival on the market back in the late ’70s, ametrine has been considered the result of irradiating and heat treating amethyst. It’s true that you can create bi-colored quartz. But natural ametrine occurs in Bolivia, near the southern states of Brazil (much of the commercial citrine we see is heat-treated Brazilian amethyst, although naturally colored citrine comes from Bolivia as well.)

Amethysts form in pegmatites (coarsely crystallized magma masses) as small to large cavities within a hard greenish rock shell called a vug. You’ve probably seen these as large decorative pieces, possibly back-lit to display the gems at the back of the shell. These formations occur during volcanic processes; as molten rock cools, these cavities are created. Minerals caught within these cavities precipitate out of the sludge and gemstones begin to grow.

Amethyst can form very large crystals weighing several pounds each, with clusters totaling hundreds of pounds. Vugs – broken open at one end or sliced into solid rings or smaller pieces – often are available for just a few dollars per pound. They make terrific displays and may even appeal to customers who want to do something a little unusual with their birthstone.

History and lore. Sources dating back to Pliny label amethyst (amethustos) as the color of wine. Because of this, it was said to protect its wearer from becoming inebriated, although some thought this worked only if you drank from an amethyst goblet. (Most modern amethyst wearers won’t depend on this talisman when drinking wine!) Amethyst also was believed to protect its wearer from all sorts of danger – including, but not limited to, poisons, passion and evil thoughts.

Don’t forget that purple is the color of royalty and that the exploits of international royalty fascinate many Americans. What better way to get closer to the royals than to wear amethyst?

Gemology. Amethyst belongs to the quartz family (formula: SIO2). Inclusions or mineral elements give rise to each variety, of which there are dozens. Purple amethyst is quartz colored by color centers of iron.

Quartzes come in all colors, if you include the cryptocrystaline (chalcedony) as well as the single-crystal mineral varieties. Here are the better known:

Rock crystal (colorless).

Amethyst (purple).

Citrine (orange, yellow).

Ametrine (bi-color combination of amethyst and citrine).

Rose (pink).

Smoky or cairngorm (brown).

Chrysoprase (translucent yellowish-green).

Carnelian (translucent orange to red and brownish-orange or red).

Agate (banded colors of chalcedony quartz).

Onyx (translucent to opaque black and white parallel color bands).

Chrysocolla (chrysocolla, a copper mineral in quartzite; translucent blue to blue-green).

Aventurine (chrome green mica platelets, fuchsite; semi-transparent green with sparkles, “aventurescence”).

Tiger’s-eye (quartz replacing crocidilite, a fibrous asbestos variety of riebeckite, creating a semi-translucent yellow-golden and brown “wavy cat’s-eye”).

Cat’s-eye (transparent brown to greenish-yellow chatoyant quartz with fine straight needles).

Fire agate (semi-translucent chalcedony showing iridescence on a botryoidal, grape-like, structure).

But of all these varieties and more, only amethyst is February’s birthstone.

Gemological properties. The refractive indices of all quartzes are in the low 1.50s; amethyst’s is 1.54. For cutters, this means greater potential for a window – a generally undesirable see-through effect – if the pavilion is not proportioned very accurately. (The lower the RI, the greater the potential window. Diamond, with an RI of 2.417, shows no window when cut in typical fashion.) Concave faceting can help reduce this seemingly uncontrollable window in quartzes.

Specific gravity is approximately 2.66. Specific gravity is a gem’s weight related to the weight of an equal volume of water. Diamond’s S.G. is 3.52; amethyst and other quartzes should look much larger (about one third again the size) than a diamond of the same weight.

Amethyst’s hardness is 7, the same as that of dust – which, like amethyst, is basically quartz. This means you must be extra careful to rinse off any dust before cleaning an amethyst with a cloth. Anything with a hardness of 7 or higher will scratch and dull the surface of amethyst.

When you look down the axis (the long direction of the crystal), amethyst shows six pie-shaped wedges of growth. Every other wedge contains the amethystine color; the intervening wedges may be colorless, amethystine, smoky/brown or citrine. This growth pattern, called the Brazil law twin, will aid in distinguishing natural from synthetic amethyst.

Treatment and synthesis. Heating amethyst can produce rock crystal, citrine or even ametrine. Care must be taken at the jewelers’ bench in order to preserve the original color. Long-term exposure of Bolivian ametrine to light will fade its amethyst color. This color can be renewed with irradiation.

Since great numbers of synthetic amethysts are on the market, you should try to determine the origin of each piece in stock. As the article “Buying amethyst today” (January 1998 JCK, page 158) pointed out, you probably already have sold a synthetic amethyst without realizing it. That article details how to detect synthetic amethyst.

Pricing. Current wholesale per-carat prices, as listed in The Guide from Gemworld International Inc., are $3-$7 for Good quality and $7-$16 for Fine quality in 1- to 3 ct. sizes. For 3- to 5 ct. amethysts, per-carat prices are $4-$9 for Good and $9-$18 for Fine.

Substitutes. A few stones can be mistaken for amethyst, so be alert to any possibilities for misidentification. Glass is an all-too-common substitute for amethyst; with its similar RI and SG, it can fool the casual glance. Two other possible switches can occur with synthetic sapphire and fluorite. Both match the color of amethyst closely, but their refractive indices, and therefore luster, are quite different. Only a keen eye can discern the differences in luster, but with practice, it shouldn’t be too difficult to make the distinction.

If you were born in February, but purple’s not your color, there are some alternatives. If you’re an Aquarian (Feb. 1-20), try garnet. There also are phenomenal gems for each day of the week, gems for the hour of day, and gems of winter; all can be found in Kunz’s The Curious Lore of Precious Stones.– Gary Roskin