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 August 2009
In our newsletter this month:
• The Green Garnets
• New and Interesting Gemstones
• Rare and Unusual Gems
• Customer Questions
The Green Garnets
When most people think of garnet, they think of the common red garnets like almandine and pyrope. But the garnet family is actually remarkably diverse. Garnets can occur in nearly any color, from brown to yellow to orange, red and purple. But the green garnets are among the rarest. Recently we've been lucky to find some excellent specimens in the market.
The garnet group is conventionally divided into 6 species: pyrope, almandite, spessartite, grossular, andradite and uvarovite. The different garnets share a similar crystal structure, but differ slightly in their chemical compositions. Green garnets are found in both the grossular and andradite species.
The grossular species includes two green garnets -- the yellow-green grossularite and the chrome green tsavorite. The name "grossular" comes from the botanical name of the gooseberry, grossularia. The garnet known as grossularite is typically a greenish-golden to yellow-green or olive-green. The rarest grossular is tsavorite, a rich green to emerald green garnet found only in Kenya and Tanzania. The outstanding green of tsavorite is thought to be due to trace amounts of chromium and/or vanadium.
Tsavorite has become a popular alternative to emerald, though tsavorite is actually the rarer stone. But the more common grossularite has its own attractions. Grossularite displays similar brilliance to tsavorite, due to a refractive index that lies midway between spinel and sapphire. But the lighter colors of grossularite tend to have better dispersion or fire.
The rarest of all garnets -- and one of the rarest of all gemstones -- is the green demantoid garnet. Particularly fine examples can command prices of thousands of dollars per carat. Demantoid belongs to the andradite variety of garnet, which is a calcium iron silicate with a refractive index of 1.88-1.94. The high refractive index makes demantoid the most brilliant of all the garnets; in fact it has a higher refractive index than sapphire and ruby. Demantoid also has remarkable dispersion or fire that exceeds even that of diamond. Indeed, the very name demantoid means "diamond-like luster."
Most of the green garnets, especially demantoid, are found only in smaller sizes. Specimens over one carat are uncommon and stones over 2 carats count as very rare indeed.
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| New and Interesting Gems -- updated November 9th |
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Watermelon Tourmaline from Nigeria: Watermelon tourmaline is one of the most distinctive gems in the world. We have just purchased a small number of exquisite pieces from Nigerian with outstanding color and clarity. These are the finest we've seen this year. |
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Boulder Opal from Australia: Boulder Opal is the second most prized form of opal, after black opal. The name derives from the fact that this opal is found embedded in ironstone boulders. Boulder opal is especially attractive because, like the black opal, it has a dark body tone which adds vibrancy to the play of color. We've just purchased a small lot of excellent pieces, in sizes between 4 and 15 carats. |
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Clinohumite from Tanzania: Clinohumite is a rare mineral. It is a member of the humite group of minerals, which includes humite, clinohumite, chondrodite, and norbergite. Only three sources of gem-quality clinohumite are known: the Pamir Mountains of Tajikistan, the Taymyr region of northern Siberia and the Mahenge plateau of Tanzania. Usually clinohumite is found in sizes under 1 carat but we just have acquired a small number of new pieces from Tajikistan in the 2-3 carat size. |
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Huge Topaz from Brazil: Gem-quality minerals are sometimes found in exceptionally large sizes. We've acquired some natural topaz from Brazil in sizes between 360 and 507 carats. We currently have 4 pieces in a light champagne color with outstanding clarity (all of been graded IF). Collectors take note. |
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Fluorite from Namibia: Fluorite is said to be the most colorful mineral in the world. We've just bought a new stock of some very colorful pieces, including electric greens and blues and some fascinating multicolor pieces. Most of the new pieces are in the 10 to 45 carat size, with a few larger stones, all with excellent clarity. We've recently added some very colorful cabochons as well. |
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Color-Change Diaspore from Turkey: Diaspore, sometimes marketed under the name Zultanite, is a color change gem from Turkey recently introduced to the international market. Under natural or fluorescent light, Diapsore has a kiwi green color, with flashes of yellow. Diaspore displays a champagne color under incandescent lighting, and when exposed to subdued lighting, such as candlelight, has a pinkish hue. We've recently bought a substantial number of new pieces, with a good choice of cuts and sizes. |
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Snowflake Obsidian from Mexico: Obsidian is a naturally occurring volcanic glass. It is formed when felsic lava extruded from a volcano cools without crystal growth.In some stones, the inclusion of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern, and this is known in the gem trade as snowflake obsidian. |
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Unheated Sapphire from Tanzania, Madagascar and Thailand: Our unheated sapphires have been very popular and we continue to increase our stock (now over 700 pieces). For the discriminating gem buyer who will accept nothing less than 100% natural, you'll find pink, blue, green, yellow and violet pieces, all guaranteed to be unheated. You may be surprised how affordable these are in the smaller sizes. |
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Seraphinite from Russia: Seraphinite is a trade name for a particular form of clinochlore, a member of the chlorite group. The dark green color of seraphinite is enhanced by a silvery and feathery shimmer caused by mica inclusions. Seraphinite was named for the seraphim, the highest order of angels, because of the feather-like appearance of the chatoyant fibers in the stone. This fascinating gemstone is a new addition our inventory. |
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Top Grade Amethyst from Brazil: We've just acquired some top grade natural amethyst from Brazil in very large sizes, ranging from about 20 to 75 carats. These are all VVS or IF clarity in the richest purple we've seen in amethyst in a long time. If you've been looking for a very special piece of amethyst, you'll want to check these out. |
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Demantoid Garnet from Namibia: Demantoid is the rarest and most valuable of the garnets, and is one of the most difficult to find of all colored gems. It is one of the few colored gemstones with a luster and brilliance similar to diamond. We have built up a stock of more than 100 pieces of Namibian demantoid, including some very fine matched pairs. |
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Amber from Poland: Amber is the fossilized hardened resin of the pine tree, Pinus succinifera, formed mainly in the Eocene epoch of the Tertiary period, about 50 million years ago. Amber has been used since prehistoric times for jewelry, amulets and religious objects. The most prized pieces contain inclusions of insects or plants or pyrites. Most amber is found in the Baltic region. We buy amber just a few times a year from our source in Poland and we've just added a new stock. |
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Turquoise from Afghanistan: Turquoise has been known and valued for thousands of years. We've bought some new pieces from Afghanistan, in an interesting variety of blue and blue-green hues. We've also found some of the popular apple-green turquoise that we first carried last year, and some superb matched pairs in blue. |
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Huge Star Rose Quartz from South Africa: We carry many large gemstones, but none as large as these Star Rose Quartz. We've collected 9 pieces over 100 carats, with the largest weighing in at an amazing 974 carats. The star effect in rose quartz is unusual in any size, but quite rare in these very large stones. |
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Axinite from Tanzania: Axinite is a group of brown to violet-brown or reddish brown minerals that sometimes occur in gem quality. Axinite is distinctive for its strong vitreous luster when polished, and its interesting pyro- and piezo-electric properties. Axinite is also popular with mineral collectors due to its unusual crystal structure. We have found a small stock of golden brown Axinite from Tanzania. |
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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, blue and gray in a variety of shapes and sizes, including a good selection of pairs and lots. |
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Blue Sapphire from Madagascar, Ceylon and Tanzania: One of the most classic of all colored gemstones, the blue sapphire is always fashionable. This brilliant and hard-wearing gemstone is perfect for any kind of jewelry. We've added many new stones to our stock of more than 400 blue sapphires, including a number of excellent cornflower blue pieces. |
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Jadeite from Burma: Jade has been known and treasured for more than 7,000 years. But only in 1863 was it discovered that jade is actually not a single mineral. What was traditionally called jade is in fact two separate and distinct minerals: jadeite and nephrite. Jadeite is the rarer and more valuable jade, with the most famous deposits coming from Burma. We have verified samples of our Jadeite at the AIGS gemological lab in Bangkok. You'll find a good range of colors in these, including white, green and lavender. |
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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 500 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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Color-Change Garnet from Tanzania and Madagascar: We've recently found some rare Color-Change Garnet from Tanzania with a dramatic color change from greenish-brown to red pink. We have a small number of pieces, mostly eye-clean, in the 1 to 2 carat size. We've added these to our substantial stock of Color-Change Garnet from Madagascar. |
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Sphene from Sri Lanka: We have added some excellent new pieces to our stock of this rare gemstone famous for its remarkable dispersion or fire. These are bright golden and green pieces in interesting shapes and cuts, including a number of rounds in smaller sizes. Sphene tends to have inclusions, but we've found a number of eye-clean pieces. |
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Emerald from Colombia: We have just received a new stock of Colombian emeralds with rich color and good transparency. These are mainly ovals and pears in smaller sizes, ideal for earrings and ring settings. |
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Rare and Unusual Gems
Each month we feature a rare and unusual gem from our inventory. This month we feature an unusual black star sapphire from Thailand.
The black star sapphires with the gold stars are found in only one location: our home province of Chanthaburi in Thailand. They are also special because they are completely untreated. Most blue star sapphires have been diffusion treatment with rutile to improve the star, but these black star sapphires tend to have a distinct star in the absence of any treatment. The 55.93 ct stone shown above is especially rare because it displays a degree of perfection that is rarely seen. From it's nearly round dimensions ( 22.36 x 20.53 mm) to its well-centred and vivid 6-ray star, this is a true collector's item.
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: |
How important is it to get a certificate of authenticity when one purchases a gemstone? Thank you for your advice. HH, UK |
| A: |
If you buy from a reputable dealer, your risk is very low. For example, we test samples of all the gems we buy, and any stone we're not sure of gets sent to a gemological lab to be checked. Some customers want the added assurance of a certificate when they purchase a gemstone, so we offer optional certification from independent gemological labs for many of our gems. Just check the "Add Gem Certificate" box on the detail page when you add a gem to your shopping cart. |
| Q: |
What is a gemstone "culet"? I'm not even sure how to pronounce it! DB, Canada |
| A: |
The culet is the tiny facet at the very bottom of many faceted gems. Not every faceted gem has a culet. In some gems the culet is closed , meaning the the tip comes to a sharp point with no facet. Often the culet facet is very small and you need some level of magnification to detect it. Strictly speaking, gemologists say that a gemstone has a culet only in the case where a small facet is cut at the tip of the pavilion. A closed culet really means no culet at all. But many people in the trade still refer to the pointed tip as the culet. And by the way, the correct pronounciation is kyoo-lit (from Latin "culus" meaning bottom).
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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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