|
 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 November 9th |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
| |
 |
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. |
|
|
|
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.
|
| 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.
|
|
| 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 |
|
|
|
|
.gif){kind=small}