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 October 2009
In our newsletter this month:
• Gem Certification from AIGS
• New and Interesting Gemstones
• Rare and Unusual Gems
• Customer Questions
Gem Certification from AIGS
The task of gem identification is often quite straightforward, and can be competently handled by any knowledgeable gemologist using standard instruments that measure properties such as refractive index and specific gravity. But there are cases which are not so straightforward, and for those you need help from a laboratory with state-of-the-art equipment and highly experienced staff.
In the past we've provided gemstone certification from the local lab here in Chanthaburi, the Burapha Gemological Laboratory. They are a competent and ethical lab, and provide an efficient cost-effective service for the busy gemstone market here.
But the local lab is not able to test every kind of stone and identify every kind of treatment. Since we sell more than 110 different gem varieties and many kinds of untreated stones, we found ourselves sending more and more gems to Bangkok for testing. After trying a number of different labs, we found a lab that could reliably certify virtually every kind of stone: the Asian Institute of Gemological Sciences, widely known as AIGS.
There are a number of cases where advanced instruments and special expertise are needed to certify a gemstone. The most frequent case we encounter is that of unheated sapphires. Unheated sapphires are identified by the presence of characteristic inclusions that would be altered by heat treatment. But it takes considerable knowledge and experience to recognize these inclusions. The AIGS gemologists have many years experience analysing sapphire, and each gem is checked by two gemologists before they will sign off on a certificate. If they are not 100% confident of their conclusions, they will not issue a certificate.
Quartz is another difficult case. Though quartz is one of the most common minerals in the world, distinguishing natural from synthetic quartz is actually a challenge, especially with very clean specimens. Many gem labs will simply issue an "undetermined" verdict when analysing a quartz sample, since they don't have the expertise to reliably identify synthetic material. AIGS has the capability to do analysis with infrared spectroscopy, in addition to microscopic analysis of inclusions and twinning.
We had another case recently where we had some black gemstones that the local lab could not identify. Based on the measurements of refractive index and specific gravity, they thought it could be garnet. We sent samples to AIGS, who were able to identify it conclusively as black spinel. Even though the refractive index seemed to be out of the normal range of spinel, analysis of the chemical composition using an EDXRF (Energy Dispersive X- Ray Fluorescence) spectrometer showed conclusively that it was an iron-rich spinel.
We use AIGS for testing samples of all new gems we buy, and especially for testing rare or unusual gems such as the Padparadscha Sapphire featured in this month's newsletter. Soon we will start offering some gems with certificates included in the price, and you will be able to view the certifcate online. |
| New and Interesting Gems -- updated August 31st |
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Ametrine from Bolivia: We've added some impressive new pieces of natural ametrine to our collection. The new pieces are mostly emerald-cut, with excellent color zoning and VVS clarity, mainly in the 5 to 8 carat size. These are the nicest ametrine we've found this year. |
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Tsavorite Garnet Pairs from Tanzania: Tsavorite garnet is increasingly rare and matching pairs in the top chrome green color are hard to find. We've acquired some very fine rounds, trillions and ovals, mainly in smaller sizes. These are ideal for earrings or ring settings. The brilliance and sparkle of these gems is remarkable. |
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Asscher Cut Gems: The Asscher cut is a special form of the step cut which has become popular for diamonds, but is rarely found in colored gems. The Asscher cut is square with dramatic cut corners, forming an octagonal outline. It is cut with a deep pavilion, resulting in an interesting geometrical windmill-like pattern when viewed from the table. We have started creating some Asscher cuts in our workshop and have produced a number of pieces in topaz, amethyst, tourmaline and smoky quartz. |
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Spinel from Burma: We buy fine spinel whenever we can find it, and we've recently added some very fine pieces of Burmese spinel. You'll find red, violet, orange, pink and blue in a variety of shapes and sizes, including a number of rare pieces over 2 carats. |
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Tourmaline from Mozambique and Nigeria: We have been aggressive buyers of African tourmaline as new material comes on the market. We now have a stock of over 3,100 pieces. Among our latest acquisitions are some very fine blue greens, some interesting multicolors, and a range of vivid pinks. |
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Spessartite Garnet from Mozambique: We have added a large number of new pieces to our extensive inventory of this very popular gem. We now have over 900 pieces in stock, in mandarin and red-orange, in both cabochon and faceted. The range of sizes and quality grades is extensive. Our most recent additions are in the best mandarin orange color, mainly in smaller sizes. |
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Kyanite from Burma: We've just purchased a new stock of faceted kyanite from Burma in a sparkling sapphire-like blue. Kyanite is usually cut as cabochons, but recently higher-grade material has been cut in facets. Like most kyanite, these exhibit the interesting color streaking which is the kyanite hallmark. You'll find ovals, pears and emerald-cuts, with many calibrated stones in the 7 x 5 mm size. |
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Kunzite from Afghanistan: Kunzite is the pink variety of spodumene, named after the famous American mineralogist George Frederick Kunz. We've been finding some lovely pieces in the market recently, with excellent color saturation. You'll find a good range of sizes and shapes, including oval, pear, trillion and cushion cut. |
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Large Green Apatite from Madagascar: Apatite are rare in larger sizes, but we have recently acquired a small number of very large green apatite from Madagascar. These are all eye-clean specimens with excellent color, ranging in size from 7 to 24 carats. We hardly ever see apatite in these size so collectors take note. |
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Fire Opal from Mexico: We always try to keep a good stock of this affordable Mexican opal, but we've recently expanded our stock with some very nice yellow and orange cabochons in a wide range of sizes and shapes. We also have some matched pairs for earrings. |
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Aquamarine from Mozambique: Aquamarine is the light blue or blue-green variety of beryl, the same gem species as emerald and morganite. Most aquamarine is quite pale, and the deeper tones are valuable and hard to find. We have just added several dozen new pieces from Mozambique in a saturated blue that is the most coveted color in aquamarine. |
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Peridot from Pakistan: Many people in the gem trade believe the finest peridot in the world comes from Pakistan. We have found a small parcel of top Pakistani peridot in very good sizes, mainly 1.5 to 4 carats. If you're a peridot aficianado, be sure to check these out. |
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Turquoise from Afghanistan: Turquoise has been known and valued for thousands of years. We've just bought some new pieces from Afghanistan, in an interesting variety of blue and blue-green hues. Among our new acquisitions are some excellent matching pairs. |
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Labradorite from Madagascar: Labradorite is a member of the plagioclase feldspar group, which also includes andesine and sunstone. Labradorite displays an iridescence in lustrous metallic tints, often blue and green. It is mainly caused by interference of light from lattice distortion. We've just bought a new parcel of fine Madagascar labradorite, with a good selection of shapes and sizes. |
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Opal from Sudan: Most of the world's precious opal comes from Australia, but there is some high quality material found in east Africa, especially in Ethiopia and Sudan. We have just acquired our first lot of Sudanese opal, with several dozen pieces displaying a good play of color. Sizes range from 0.5 to 3.6 carats. |
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Chrysoprase from Tanzania: Chrysoprase is considered the rarest and most valuable stone in the chalcedony quartz group. That's quite a distinction considering that the chalcedony species includes agate, chalcedony, onyx, carnelian, bloodstone and jasper. But chrysoprase, it is fair to say, is also the least known of all the chalcedony varieties. Chrysoprase is a vivid apple-green to emerald-green, colored by trace amounts of nickel, and can look very impressive when set in jewelry. |
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Rutile Quartz from India and Brazil: Rutile (or rutilated) quartz is clear or smoky quartz with inclusions of rutile crystals. Rutile is the mineral name for natural crystals of titanium dioxide. While most varieties of transparent quartz are valued most when they show no inclusions, rutilated quartz is valued specifically for the lovely patterns formed by the delicate golden needles of rutile inside it. We've just purchased an interesting lot of faceted pieces from India to add to our stock of Brazilian material. |
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Large Blue Topaz from Brazil: High quality topaz can sometimes be found in very large sizes, and we have just purchased a small number of blue topaz over 100 carats. Several of these weigh in at over 200 carats, These unusual stones display the same vibrant color and excellent clarity that you'll find in more ordinary sizes. |
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Rare and Unusual Gems
Each month we feature a rare and unusual gem from our inventory. This month we feature a very rare unheated Padparadscha Sapphire from Tanzania.
The rarest and most valuable color in sapphire is called Padparadscha. The name is said to derive from the Sinhalese term for lotus flower. The color is subtle, but the rule is that a true Padparadscha sapphire must display both orange and pink hues with a pastel tone. Since the elusive color is so rare, sapphires that display this color without the help of any treatment are especially prized. In fact many connoisseurs would argue that a true Padparadscha must always be untreated.
This 1.06 carat orange pink sapphire from Tanzania has been certified by AIGS as an unheated Padparadscha sapphire (view the certificate for this gem). It is a stunning gem, with a delicate balance of orange and pink. It is also very clean and we've graded it VVS (almost loupe clean). Truly a rare stone.
Customer Questions
Every month we answer questions of general interest from our customers. Please feel free to send your questions to help@gemselect.com. |
| Q: |
What is the most common shape for gemstones? Is it round? I am looking for square gems but I don't find many of them. Thanks for your answer. JT, Netherlands |
| A: |
Gem cutters generally choose a shape that will preserve the most of the rough stone. Based on that principle, it turns out that the most common gemstone shape is oval. You'll find that about 35% of the gems in our inventory are ovals. Round gems are very popular, but cutters have to sacrifice more raw material to cut round gems. The same is true for square gems. You'll find that we have a large stock of square gems, with more than 900 items in stock. It's also worth looking at our octagon shape gems, since a number of these have proportions which are nearly square.
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| Q: |
I see you have some gorgeous jasper pieces from Indonesia. Could you tell me more about them, please? CB, UK |
| A: |
Southeast Asia is famous for gemstones, but one usually thinks of Burma, Thailand and Cambodia, not Indonesia. There is a small but significant gemstone industry in Indonesia, centred in Kalimantan, the Indonesian part of the huge island of Borneo. Gemstones discovered there include diamonds, ruby, sapphire and amethyst, but the region is most famous for its enormous variety of agate, jasper and chalcedony. Every time we buy the Indonesian jasper we find new patterns, colors and designs.
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| A final note -- If you send us email, please be assured that we answer all our email very promptly, 6 days a week. But we sometimes have problems with spam filters on the receiving end, so please adjust the settings on your mail client so you can receive mail from help@gemselect.com.
Happy gem hunting,
Your friends at GemSelect |
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