Getting a Better Fix On Emerald Fillers
Now that it’s common knowledge nearly every emerald is clarity-enhanced, jewelers and consumers alike want to know just how effective and stable the enhancements are. They also want to know which treatment has been applied to their stone. And, if given a choice, they’d like to know which is the best to use. Researchers at the Gemological Institute of America are trying to provide some answers.
Last year, GIA’s researchers set out to determine which emerald fillers are being used, the stability of each, and how to identify them. They reported the first part of their study, which clears up the gemological nomenclature and lists the properties of fillers, in the Summer 1999 issue of Gems & Gemology. It’s a useful report. Here’s a brief summary.
Fill ’er up. Led by Dr. Mary Johnson, GIA’s research staff has listed the properties of emerald fillers, and the results are overwhelming. But finding out what’s being used was a difficult task in itself.
Literally thousands of products can be used to fill emerald fractures; the diverse list includes 3-in-1 oil as well as whale oil. The first hurdle for GIA was to narrow the study to 39 enhancements considered the most common—those that are readily available, that are known to be in use, or that otherwise possess identifying features.
The next step was to classify the enhancements and dispel the confusion over what jewelers were calling “oil,” “natural,” “resin,” and “epoxy-resin,” including “Opticon-type” and “synthetic.”
The term “natural” should be avoided, because many natural substances can’t be separated from their manufactured counterparts (that is, synthetics). Nor should the term “synthetic” be used, since chemists and gemologists define the term differently. (For chemists, any lab-created polymer is “synthetic,” whereas for gemologists, a “synthetic” substance has a natural counterpart). “Epoxy-resin” likewise is misleading, since many resins don’t contain epoxides. Also avoid the phrase “Opticon-type,” since Opticon is a trademarked and patent-specific resin. In some cases, it may not even be possible to identify a filler, since there are artificial resins with “natural” spectra as well as mixtures of different fillers that hide characteristic spectral features.
The GIA researchers came up with a more accurate terminology. Based on the structures and compositions of the various compounds, they devised six categories of fillers in two main groups, “presumed natural” and “artificial resins.” Substances that are presumed natural include “essential oils” and “natural resins” (such as cedarwood and Canada balsam), “other oils” (such as mineral and paraffin oil), and “wax” (paraffin wax). Substances considered “artificial resins” include “epoxy pre-polymers” (such as Opticon Resin 224, Araldite 6010, and Epon 828), “other pre-polymers” (such as Norland Optical Adhesive type 65), and “polymers” (including Permasafe, Super Tres, and cured Opticon Resin 224).
The better mask. The closer the refractive index of these enhancements to emerald’s approximate 1.57, the better the filler will mask the fissures. The researchers tested the refractive indices of all 39 enhancements, and surprisingly, the fillers used most commonly today are not necessarily the ones with an R.I. closest to emerald’s. For example, cedarwood oil’s R.I. is 1.52. However, the epoxy pre-polymers Araldite 6010 and Epon 828 and the polymers Permasafe and Opticon do have R.I.’s very close to emerald’s.
Does this mean they’re the best enhancements? Not necessarily. Stability and durability have yet to be studied. Stay tuned for Part II, which GIA is working on now.
In the meantime, how can you identify which filler was used in your emerald? This, as the GIA researchers discovered, is not easy. Seeing the “flash effect”—the filler showing flashes of blue and yellow under dark- and light-field magnification—indicates only that a filler is present. The flash effect can’t identify the enhancement. So GIA, like other high-tech laboratories, uses infrared and Raman spectroscopy to attempt identification.
The 39 fillers were tested (outside an emerald) to determine their properties. Then they were mixed in numerous proportions (as would be the case inside a typical emerald) and tested again. GIA researchers discovered that many times small amounts of a second filler are not visible in test results, which makes identification impossible. When you relate this information to the minute amount of filler inside an emerald’s fissure, where the identification process is even more difficult, the GIA Gem Trade Lab’s reluctance to identify fillers is understandable.
One filler conspicuously missing from GIA’s list is Arthur Groom’s Gematrat. While Groom supports GIA’s research and helped clean out the enhancements of the emeralds tested in this project, he opted not to have his filler tested in Part I for fear of having proprietary information published. But you’ll see Gematrat-enhanced emeralds in the next and more important part of the study. Groom expects his filler to eclipse all others in durability and stability.
Amami Golds: South Seas Size With Japanese Luster
Even while controlling 70% of the world’s mabé pearl market, in the past 15 years Tasaki Shinju Co. quietly has been developing and harvesting South Seas-sized golden pearls. Now the Kobe, Japan-based company is ready to make some noise.
Tasaki Shinju will start promoting necklaces, earrings, and other items featuring Amami gold pearls under the Amami Gold brand. The firm plans to ship just over 50,000 of the pearls this year and will market 150 necklaces along with earrings and pendants in Japan. Prices of the necklaces range from $4,500 to $45,000, depending on the size and quality of the pearls.
Although Tasaki Shinju is promoting them as South Seas pearls, the company is culturing the golden pearls in gold-lipped oysters (Pinctada maxima) in the bays of Amamioshima in Japan. Amamioshima—Amami for short—is an island at the northern end of the Ryukyu Islands chain, south of Japan’s big islands. Until now, the farthest north these oysters have been cultivated was the Philippines, more than 1,000 miles to the south.
D’Elia & Tasaki of New York, which represents Tasaki Shinju, has been selling the Amami golds in small quantities for about 10 years. Because they’re grown in Japanese waters, they have the benefits of South Seas size with Japanese quality, says Brady D’Elia. “Traditionally, South Seas pearls are grown in warmer waters, allowing for greater nacre thickness and yielding a larger pearl,” says D’Elia. “What we give up in size, we get back 10-fold in luster.” The colder Japanese waters allow for thinner, more even, less spotted, and more lustrous nacre, typical of the Japanese akoya. The Amami golds are slightly larger than Japanese akoyas, averaging 10 mm or more in diameter.
Colorful Gem Enhancement
One of the latest and certainly more interesting enhancements to gemstones these days is Bart Curren’s gemstone enameling. Curren, owner of Glyptic Illusions in Vancouver, B.C., Canada, ranks among North America’s top gem artists.
“I’m currently using only two gem materials to enamel: basalt and quartz,” he says. Basalt has been his mainstay. Most of his earlier pieces were carved of basalt. “I’ve had the idea for a long time, but I wanted to use true enamels.” Using a new product called “low-temperature enamel,” Curren now can create his long-awaited design.
“Basalt has a large glass content, so I thought it might work to enamel basalt,” says Curren. But he found that true enamel was a lot more difficult to work with. “It’s too labor-intensive.”
The rock crystal quartz was just an afterthought. “But people really like it,” he says. With the quartz, he applies enamel to the pavilion. “Through the frosted quartz, the enamel adds a real interesting glow,” he says. Because of this striking appearance, Curren believes the quartz will be more readily accepted.
Since the unmounted basalts appear somewhat unusual, Curren is putting stone bails on the reverse. “They just looked like they needed to be finished,” he says. Now that they are, the response has been more positive. The enameled gems sell for a suggested retail price range of $120 to $250 and are available through Gem Reflections of California, San Anselmo, Calif., (415) 454-8233.
Chrysocolla and Gem Silica: Arizona’s Rare Hidden Treasures
Arizona is a copper-producing state, at one time ranking among the world’s major sources of the metal. It’s that same copper that gives minerals like chrysocolla and gem silica their striking blue color.
Chrysocolla is not one of your better-known gems. That’s mainly because it’s not as common as you might expect for an ornamental stone. Nor is it durable enough as a gem material by itself. But it is very beautiful, and under the right circumstances it can be a very wearable stone.
Chrysocolla has been the subject of great confusion in gemological circles. Many don’t realize that it’s actually its own mineral, a copper silicate. With a hardness of 2 to 4 on the Mohs scale, this doesn’t make it one of your more practical gems. But since it crystallizes in so many different compositions—mixing with quartz, turquoise, malachite, azurite, and chalcedony—its hardness can reach a very wearable 7.
In fact, most gemologists never see chrysocolla by itself, but only as an inclusion in one of these other gem materials. While a more accurate name would be, for example, “chrysocolla in chalcedony,” most simply refer to it as chrysocolla, claiming it as a variety of chalcedony.
Pure chrysocolla, without the quartz or chalcedony matrix, is “nice stuff,” says Charles Vargas of Apache Gem in San Carlos, Ariz., an expert in Arizona gem materials. The gems become hard enough to cut only when encased in harder materials, such as the quartzes, including chalcedony, a cryptocrystalline quartz.
Follow the copper. The landscape of Arizona’s copper deposits, the source of chrysocolla, is “riddled” with volcanic vents, says Vargas. “The hot water quartzes shoot through the copper vents, where the copper and silicates combine to create gems,” he says. Once they’re intermixed, the chrysocolla in chalcedony silicate makes a beautiful gem material.
San Carlos, 100 miles east of Phoenix, is a major copper-mining area. Other areas of copper minerals include Bisbee, south of Tucson near the Mexico border; Morenci, just 5 miles east of the San Carlos Apache reservation (almost in New Mexico); and Globe and Superior, 50 miles east of Phoenix. The U.S. quality is rated as the finest in the world. Gems from Miami Inspiration, an open-pit copper mine 5 miles west of San Carlos, are considered the best of the best. “There are experts who can identify the origin of these chrysocollas just by their structure,” says Vargas.
Bubble, or botryoidal material, generally shows a clear chalcedony cap. But it’s unpopular because of the thickness of the chalcedony, and it’s worth only about $2 to $5 per carat. Druzys are more popular, with the more commercial material generally priced at $3 to $7 per carat. Druzy can fetch as much as $20 per carat.
The more common chrysocolla in chalcedony is the broken-patterned material. “It looks as if it’s been hit by a hammer and glued back together” with semi-transparent chalcedony, says Bruce Barlow of Barlow’s Handcrafted American Gemstone Collectibles in Phoenix. Barlow is a leading expert in chrysocollas and gem silica. “It’s a picture of an earthquake in time and history.”
Modern mining sounds death knell. “Over the last 100 years, [miners have] depleted the rich ore bodies,” says Vargas. He laments the passing of the old days of hand-operated mining. This was the era that defined the American Southwest, settled by those using pick, shovel, and donkey. Since the advent of mechanical mining with large, automated processes, the gem chrysocolla is being destroyed.
“When you have men in the pit with the ore, you find the gems in time to recover them” before the copper is extracted, explains Vargas. The old methods enabled miners to access the higher-grade ores and remove the gems from the matrix, saving up to 90% of the gems. Now, “you crush the mountain and leach it, chemically releasing the copper,” he says. Once crushed, the gem chrysocolla is gone.
To find some of the nicer chrysocollas, the trade is falling back on old holdings of material, passing on family collections, and searching through yard sales and estate sales. Vargas says that mining changes in the metals deposits have resulted in the loss of more than 5,000 jobs. “This will have a huge effect on the gem trade, too,” he warns. “Of course, the Chilean and Chinese chrysocolla will continue to be available, since the mining in these areas is still done by hand.” Meanwhile, the beautiful pure blues and powder blues of the American Southwest will soon become American gem history.
Gem silica. Gem silica is chalcedony in chrysocolla. Certain ranges of silicates fall into the category of “gem,” says Barlow. “It was very popular in the late ’70s. The top stuff really came out in the 1940s. Most of it came from the Live Oak tunnel in Globe, now one of the open pits called the Miami-Globe mine. Next would be the Ray copper mine, southwest of Globe. Of late, it’s just the Ray mine material that’s available, and it’s not real pure and clean like the old Globe silica.”
Interestingly, the biggest consumer of gem silica has been Taiwan. Gem silica has the appearance of some jade materials. The United States has better-quality silicates than those found in Taiwan. The finest quality gem silica has garnered prices up to $3,000 or more per pound (roughly $1.50 per carat).
All gems courtesy of Nadiene Nelson at Mississippi Pearl Jewelry Co. Nelson is an expert in native American gemstones. She can be reached at (305) 872-4717 or via e-mail at PearlQueen@aol.com.