Amethyst is a staple item in every jewelry store. This February birthstone can possess a beautiful royal purple color, yet remain very inexpensive. Amethyst is relatively hard on the Mohs scale at 7, is readily available in all sizes and shapes and often comes in designer cuts and carvings.
So, what’s the problem? The problem is that jewelers unknowingly sell many synthetic amethysts. This is not a theory; it’s a fact. You have done it.
The demand for honest representation must start with the retailer. Jewelers who learn how to separate the genuine from the synthetic can help the industry find deceptive sellers and put them out of business. This article explains how to do it; it also tells how to grade and price genuine amethyst.
Sources: Although amethyst comes from many sources, Brazil remains the primary location. Yet Russia and Africa have yielded some of the finest amethyst. Russian material, once known as Siberian amethyst, is no longer being produced, but African stones are very popular due to their rich purple colors and reddish overtones. Amethyst has been mined in Zambia, Tanzania and Namibia, with Zambia the primary producer. Supplies from Africa remain tight and prices are high.
South American stones are readily available in all sizes and shapes. Their colors aren’t as good as those of African stones, but they satisfy a niche market for millions of consumers worldwide. African stones generally offer a more saturated hue; some stones actually are over-saturated and appear too dark. Because of the popularity – and short supply – of African stones, amethyst from other locations often is brought overseas and represented as Zambian.
The birth of synthetic amethyst: Synthetic amethyst was originally developed to meet demand for untwinned quartz crystals during World War II. Genuine quartz usually grows in twinned crystals; untwinned crystals were needed for oscillators used in radios. By 1950, great quantities of synthetic amethyst were being produced by the hydrothermal method. Today these synthetics are used for radios, watches and other electrical applications. Synthetics for the jewelry industry were first grown in Russia, then Japan and China. They’ve been commercially available since about 1970.
Synthetic amethyst is inexpensive: most faceted stones sell for a few dollars per carat. However, prices for natural amethyst also are low, averaging only about $10 per carat. Because of these low prices, historically little testing of amethyst has been done. This led to the “salting” of parcels, with synthetics mixed in with the genuine. Roger Dery of Spectral Gems in Birmingham, Mich., says he knows first hand of salting as far back as 1985, 15 years after synthetic production began. But no one was talking about it and jewelers buying amethyst were unsuspecting.
Today testing remains minimal and salting has increased. It’s estimated that as much as half the amethyst now on the market is synthetic. Jewelers, still unsuspecting, routinely buy it.
(Note that synthetic quartz is being made in all colors including green, rose, amethyst and citrine; see photo 1. Although this article focuses on amethyst, jewelers should be cautious of all quartz varieties.)
Eric Braunwart, Columbia Gem House Inc., Vancouver, Wash., confirms the use of synthetics in mass production lines. “In some instances, manufacturers are paying the same price for synthetic rough for which they can buy genuine rough. But when they need to produce 100,000 stones, all matched, and they get twice the yield from synthetic rough, it becomes much more profitable to use the synthetics.” He adds that synthetic rough is used for mass production of other colors, colorless and smoky quartz.
Spotting the genuine: When the industry first learned of synthetic amethyst, jewelers hoped for an easy detection test. The information that GIA originally provided to the trade included a test known as “Brazil-law twinning.” Most synthetic amethyst was grown from untwinned seed plates and didn’t show this Brazil twinned pattern when viewed under crossed polars. But a later article in Gems & Gemology questioned the value of this test since some synthetic material now was being grown in twinned crystals. Today jewelers must rely more on magnification and other features to help with the separation.
To begin, do not try to identify synthetic amethyst based on color alone. Synthetic amethyst is being made in a variety of colors. Jewelers recently have told me they were suspicious only of very fine amethyst because they knew the lighter tones had to be natural. That is completely incorrect; I personally possess samples of synthetic amethyst in varying shades of purple.
Magnification is the first key to separation. Since amethyst is a TYPE II gemstone by GIA’s classification system, much of the material will exhibit inclusions. Typical inclusions may be well-defined crystals (photo 2), fingerprint-type inclusions possibly in intersecting planes (photo 3), or “zebra-stripe” inclusions (photo 4).
Although inclusions may be similar in synthetic and genuine amethyst, this is rare. For example, liquid-filled fingerprints may be found in synthetics. The typical inclusion found in a synthetic is known as a “bread crumb” (photo 5). These are very tiny and irregular in shape. They often can be located only with high magnification, so using 30X, 45X or higher is advisable. This type of inclusion is rare in natural amethyst. Also possible (although rare) in synthetic stones are “nailhead” spicules, associated with the hydrothermal process.
If an amethyst lacks identifying inclusions, you may study other characteristic features. Although exact statistics are not available, it’s estimated that only a small percentage of synthetic material is grown from twinned crystals, so testing for Brazil-law twinning may still be helpful.
Zoning is another key. Color zoning may be present in a natural amethyst, usually as zones of purple, violet-blue or colorless. Banding will be straight or angled in two or three directions. Color zoning in synthetic amethyst is more irregular and consists of lighter and darker shades of purple. Zoning can be deceiving, so examine many known samples. Indeed, experience is crucial for all identifying characteristics described.
Industry testing: An inexpensive test for synthetic amethyst was developed by the AIGS laboratory in Bangkok. Kenneth Scarratt recently acquired the testing procedure along with the lab, now called the Center for Gemstone Testing, from the Ho family. The test costs as little as $1 per stone in quantity.
Although affordable, testing is done only overseas, which has discouraged retail jewelers from sending stones. Some large manufacturers have used these services. But since the costs of testing their entire production of thousands of stones per day would quickly add up, they’ve tended to use it for random sampling to check their sources.
Since most jewelers do not force testing by their suppliers, we know that synthetics are still being sold. The quantities available are staggering, with estimates of millions of carats. One dealer informs me that a shipment of 900 kilos of synthetic amethyst recently arrived from Russia.
The American Gem Trade Association has made synthetic amethyst a priority and would like to force industry testing. AGTA’s Industry Rules Committee, chaired by Roland Naftule of Nafco Gems Ltd., is working with GIA. Members are supplying samples of many known origins for GIA’s research team to study in developing an inexpensive test similar to AIGS’s for use in the U.S. Once testing is in place, AGTA plans to push for all members to use it. As the test becomes publicly known, retailers also will be compelled to act. Testing is truly in their best interest. Finding just one synthetic in their inventory can lead to litigation and permanent damage of reputation.
Since testing is now voluntary, impractical for many and not demanded by retailers, few manufacturers do it. Eric Braunwart, a member of the AGTA committee, is very concerned about the issue. In an attempt to come as close as possible to a 100% guarantee on his own goods, Braunwart buys only rough, all of which is examined to assure it is genuine. If any synthetic is found, he rejects the entire parcel. He examines the crystal faces and inclusions. He also uses the Bangkok laboratory to spot check material and confirm his own separations. To spot check the lab as well, he includes some synthetics; to date, the lab has identified the stones. Braunwart admits that most companies don’t go through all this because of the cost, but he feels it is necessary because of the high percentage of synthetic material being sold today.
Josh Hall, vice president of Pala International, Fallbrook, Calif., is another AGTA member concerned about synthetic amethyst. Pala purchased several kilos of fine Zambian rough several years ago when it had the opportunity. It examined the rough to ensure it was genuine and does its own cutting. “Once the rough is gone,” says Hall, “we will only buy guaranteed material from known suppliers – fellow AGTA dealers, if possible.”
Amethyst grades: Amethyst can be classified into four grades – commercial, good, fine and extra fine.
Commercial grade applies to most of the stones on the market. They are often very pale in color (lighter tones and less saturated). Color zoning may be present and obvious; a grayish color also may be present. In GIA GemSet color nomenclature, these stones often are described as Purple hue, medium light tone, slightly grayish saturation or similar notation.
Good amethyst will begin to be darker in tone with less gray present. Some color zoning may still be present. A typical description could be Purple hue, medium tone, very slightly grayish saturation.
Fine amethyst will again be more saturated with optimal tonal values. A description could be Purple hue, medium dark tone, strong saturation.
Extra fine stones are highly saturated. Some may consider them too dark, but the rich saturation usually makes up for this. Ideally, some additional hues of blue or red may enhance the overall color appearance. A typical description could be bluish Purple hue, dark tone, and strong saturation.
The chart on page 160 includes photos of each grade and gives current wholesale prices for different sizes of genuine amethyst.
Pricing: Quartz is very plentiful and large crystals are routinely mined. Jewelers will find supplies good in all sizes and qualities except the truly extra fine. Prices begin to drop for very large stones over 25 carats. Finding stones of 100 carats or more is not unusual.
Minute inclusions are common. While eye-visible inclusions decrease grades and prices, very clean stones do not fetch much of a premium. A few natural inclusions actually are beneficial for identification purposes.
Several years ago, I purchased some synthetic amethyst for my laboratory. The faceted stones weighing 2-5 carats each were $4.50 per carat. Today, with mass production, prices can be even lower. Natural material, meanwhile, can reach $40 per carat for 5- to 10-ct., highly saturated material (although very little such quality is available).
The chart above shows how synthetics have affected the price of natural amethyst. It reflects the average price per carat for 3-ct. amethysts in each of the four quality grades over the past 15 years. The rise in prices in the late 1980s to 1991 was due to the popularity of African stones coming to market in highly saturated colors. Prices began to drop in the early 1990s, as synthetic amethyst became known within the industry. Recent stories of mass production and increased salting of parcels have reduced prices further. I believe that mandatory testing and an end to synthetic material being sold without disclosure would increase prices for amethyst.
Buying tips: Most jewelers will do very well selling good to fine amethyst with an average price of about $10 per carat. Some deals are usually available at major events such as the Tucson gem shows in February. However, be advised that when prices seem just too good to be true, something may be wrong. For example, if you’re offered a parcel of extra fine, carat-size amethyst for $7 per carat, this may suggest synthetic or a mixture of synthetic with genuine. Our human nature wants us to believe that we are getting a great deal, but that’s rarely the case.
References: Crowningshield R., Hurlbut C., Fryer C.W. (1986) “A Simple Procedure to Separate Natural From Synthetic Amethyst on the Basis of Twinning.” Gems & Gemology, Vol. 22, No. 3, pp. 130-139.
Koivula J.I., Fritsch E. (1989) “The Growth of Brazil-Twinned Synthetic Quartz and the Potential for Synthetic Amethyst Twinned on the Brazil Law.” Gems & Gemology, Vol. 25, No. 3, pp. 159-164.