Macau International Jewlery & Watch Fair
February 28, 2008 - March 2, 2008 |
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product and review Diamond Gem Jewelry Bracelet Ring Earring Connecticut Gemstone Repair Ruby Emerald Sapphire Precious Stones Goldsmith Bands Baguette Princess Trillion Marquise Radiant Oval Heart Pendants Pearls Platinum for sell or buy in retail store.
Macau International Jewlery & Watch Fair
February 28, 2008 - March 2, 2008 |
Organiser: | MJS Trade fairs (Macau) Limited |
Venue: | The Cotai Strip Convention and |
Phone: | 852-3428-2626 |
Fax: | 852-3105-0036 |
Email: | |
Website: | |
Description: | The ¡§Macau International Jewelry & Watch Fair 2008¡¨ has been specially arranged to be held in March, to fully capture the important opportunities of the prime period when a number of international trading exhibitions are being performed in Hong Kong and the Southeast Asia, and tens of thousands of international buyers will be visiting the region. By leveraging the advantage of accumulations of various products, the ¡§Macau International Jewelry & Watch Fair 2008¡¨ fully meet with the one-stop purchase requirements of buyers of various categories of products, and will be the target of buyers from the southern regions of the PRC as well as from the overseas. This brand-new exhibition is an ideal platform where international buyers can initially purchase their target products, and will become an important stop in their procurement tours around Asia http://www.diamondworld.net/fairs/fair_detail.asp?fairid=186 |
GJX Gem & Jewelry Show
February 6, 2008 - February 11, 2008 |
Organiser: | Gem & Jewelry Exchange LLC |
Venue: | GJX Pavilion, Tucson Show, |
Phone: | (1) 520 8824200 |
Fax: | (1) 520 8824203 |
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Description: | The Gem & Jewelry Exchange show will be held at 198 South Granada location in downtown Tucson, February 6-11, 2008. http://www.diamondworld.net/fairs/fair_detail.asp?fairid=25 |
Inhorgenta Europe 2008
February 15, 2008 - February 18, 2008 |
Organiser: | Messe Munchen GMBH |
Venue: | New Munich Trade Fair, |
Phone: | (+49 89) 9 49-01 |
Fax: | (+49 89) 9 49-09 |
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Description: | inhorgenta europe 2008 will welcome the international timepiece and jewelry world for the 33rd time on the grounds of the New Munich Trade Fair Centre from February 15 to 18, 2008. In addition to innumerable highlights in the segments of jewelry, gems, pearls and technology, numerous watch novelties will be in the focus of attention. inhorgenta europe will especially demonstrate its excellent competence in this important high-volume market of fashion and lifestyle watches. |
China International Gold, Jewellery & Gem Fair - Shenzhen
February 28, 2008 - March 2, 2008 |
Organiser: | CMP Asia Ltd |
Venue: | Shenzhen Convention & Exhibition Center (SZCEC) International, Fuhua 3rd Road, Futian District, |
Phone: | (852) 2516 1677/ 2516 1636 |
Fax: | (852) 2802 9934 |
Email: | |
Website: | www.jewellerynetasia.com/exhibitions/default.asp?siteid=2〈=1 |
Description: | Shenzhen, China's jewellery manufacturing centre, and the perfect place for international and Chinese buyers and suppliers to do business |
30th, GLDA Tuscan Gem & Jewellery Fair
February 5, 2008 - February 10, 2008 |
Organiser: | G.L.D.A. Office |
Venue: | Starr Pass Marriott Resort |
Phone: | +(520) 792 9431 |
Fax: | + (520) 882 2836 |
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Description: | The world-renowned G.L.D.A. Tucson Gem & Jewelry Show, has been held in Tucson for the past 29 years. The 2008 show will begin a day ahead of the other major Tucson Shows and end on February 10th. This show will give buyers a head start on selection and convenience as well as the most luxurious setting in Tucson, the new J.W. Marriott Starr Pass Resort. This show is the "cream of the crop" with large numbers of very competitive and direct source exhibitors and groups from all over the world for your shopping pleasure. The same high quality companies that have exhibited at the G.L.D.A. Shows for the past 29 years will be exhibiting at the new Marriott location along with many other high quality new companies and groups who have not been able to exhibit at past Tucson shows due to the shortage of quality booth space http://www.diamondworld.net/fairs/fair_detail.asp?fairid=159 |
J.C. Penney faces low sales
Sale of jewellery dipped in Q4GIA alumni Meet
The agenda focused on education about diamonds and gemstonesCharles & Colvard Ltd., had a disappointing net sales in the year 2007. During the year it faced a net loss of $24,424 as compared to a net profit of $6.1 million a year earlier.
For the fourth quarter ending December 31, 2007, net sales decreased by 35% to $7.9 million, while for the entire year it dipped by 32% to $27.81 million.
The net loss in the quarter amounted to $1.1 million, whereas it has earned a net income of $1.3 million, per diluted share in 2006. The company said they faced problems with their distribution model. In the US, sales in the fourth quarter dipped by 40% to $6.6 million, while international sales increased 20% to $1.3 million. Charles & Colvard has decided to discontinue its policy of providing future guidance on sales, gross profit margins and marketing and sales expenses.
http://www.diamondworld.net/newsroom/news.asp?newsid=2027
At the two-day International Diamond Manufacturers Association (IDMA) retreat in Israel, the members unanimously discussed the lack of cohesive and comprehensive generic diamond promotion, and expressed readiness to coordinate such a programme on behalf of the industry. The IDMA issues a statement at the meeting. The IDMA members present were, Jeffrey Fischer, IDMA president; Vasant Mehta, IDMA vice president (GJEPC of India); Moti Ganz, IDMA vice president, Uri Schwartz, Bumi Traub, David De Toledoand Udi Sheintal (the Israel Diamond Manufacturers Association); Eduard Denckens, IDMA vice president; Maxim Shkadov, IDMA vice president, Stephane Fischler, IDMA Secretary General and Treasurer, and others from diamond cutting and manufacturing bodies.
IDMA President Jeffrey Fischer affirmed that as the industry shifts to a demand driven model, IDMA has identified the lack of cohesive and comprehensive generic diamond promotion in the consumer market as a short-sighted failing on the part of the industry. " IDMA has resolved that it will take a leadership role in developing specific proposals to help remedy this situation. IDMA is calling upon all stakeholders to assemble with the express purpose of creating an ongoing industry-wide generic diamond promotion campaign. IDMA offers to act as the coordinator of this 'summit meeting' to address this important need and will announce a plan of action shortly," he stated.
Fischer said. " IDMA is concerned that current rough diamond prices are speculative. As a result, the diamond manufacturing sector is experiencing the collapse of already very thin profit margins. Producers - large and small - should take note and take appropriate action!”
The participants focused on internal organisational planning, matters of concern to IDMA membership, and issues confronting the wider diamond industry. The retreat was moderated by Chaim Even-Zohar of Tacy Consultants Ltd., and Charles Wyndham of WWW International Diamonds Ltd.
Tourmaline occurs in the widest array of colors of any gemstone species. Sometimes as many as two or three colors exist in the same cut stone. Tourmaline is also known under different names: The “rubelite” is red, sometimes with a violet tint. Fine “chrome” tourmaline has a beautiful rich green color. “Indicolite” ranges from very light to dark shades of blue, violet blue, and greenish blue.
The name “tourmaline” has its origins in the Sinhalese word “Turmali”, which means mixture. Originally, native miners applied this term to mixed parcels of gems when they didn’t really know what the stones were.
Tourmaline is sometimes known as an alternative birthstone for October, and the accepted anniversary gemstone for eight year of marriage.
While tanzanite ranges in color from pale lilac to deep intense blue, each stone gives you three colors. From one angle, you may see it as a brilliant blue; turned in another direction, the color will show a purple almost as lovely as fine amethyst; turned a third way, the color will show a salmon-pink brown.
Tanzanite is one of the newest gemstones; it was named in 1967, when the first beautiful crystals were discovered in Tanzania. Because it comes from only one location and is relatively rare, it bestows on its owner a mark of distinction. Tanzanite is still young, so there is no folklore connected with it.
To maintain its brilliance, clean in jewelry cleaner or lukewarm water, do not use a home ultrasonic cleaner or subject to steam. Avoid hard knocks and scratches as well as extreme temperature changes.
Imperial topaz is the accepted anniversary gemstone for the 23rd year of marriage. Topaz is mainly found in Brazil, Nigeria, and Sri Lanka.
Most people think of topaz as a transparent golden yellow gemstone. However, this gemstone also occurs colorless as well as orange yellow, red, honey-brown (dark sherry), light green, blue, and pink. The name topaz is derived from the Greek word meaning “to shine” and also implies “fire.” Orange-red “Imperial” topaz and pink colors are rare and most valuable.
The lore, magic and romantic of topaz goes back many thousands of years. It holds the distinction of being the gemstone with the widest range of curative powers. Ancient Egyptians thought its golden glow symbolized “Ra,” their sun god. The Greek felt it gave them strength. In addition, it supposedly cooled tempers, restored sanity, cured asthma, relieved insomnia and even ward off sudden death. Topaz is said to make its wearer invisible in times of emergency. It proved the loyalty of associates by changing color in the presence of poison.
Grape Garnet describes an intense purple-red variety of garnet that is distinctively different in color from ordinary rhodolilte or amandine garnet.
Mined in the Orissa of Northwest India, Grape Garnet constitutes only a minute fraction of the massive Indian garnet production. Due to primitive mining methods and a short mining season interrupted by torrential monsoons, this stone variety is not widely known outside its local area. Historically we see examples of this material as badly faceted, dull purple stones in silver jewelry or as beads. But careful selection of rough stones and precision faceting bring out its unique fire and color. The result is an intense purple-red hue that flashes and sparkles even in very limited light, and positively comes alive in sunlight.
Blue topaz is one of the accepted birth stones for December and anniversary gemstone for 4th year of marriage, and Imperial topaz for the 23rd. Topaz is found mainly in Brazil, Nigeria, and Sri Lanka.
Most people think of topaz as a transparent golden yellow gemstone. However, this gemstone also occurs colorless as well as orange yellow, red, honey-brown (dark sherry), light green, blue, and pink. The name topaz is derived from the Greek word meaning “to shine” and also implies “fire.” Orange-red “Imperial” topaz and pink colors are rare and most valuable.
The lore, magic and romantic of topaz goes back many thousands of years. It holds the distinction of being the gemstone with the widest range of curative powers. Ancient Egyptians thought its golden glow symbolized “Ra,” their sun god. The Greek felt it gave them strength. In addition, it supposedly cooled tempers, restored sanity, cured asthma, relieved insomnia and even ward off sudden death. Topaz is said to make its wearer invisible in times of emergency. It proved the loyalty of associates by changing color in the presence of poison.
Citrine is one of the accepted birthstones for November, as well as the anniversary gemstone for the 13th year of marriage. It is found mainly in Brazil.
Citrine is a variety of quartz; colors range from pale yellow to yellowish-brown and “Madeira” red. The most popular fashion colors are the vivid yellows and oranges. It is often mistaken for yellow or golden topaz. Citrine is readily available, very affordable in large sizes and stands up well to daily wear. Its earthy tones complement many wardrobes. Citrine is often seen in jewelry combined with amethyst, blue topaz and pink tourmaline.
Citrine’s name is derived from “citron,” a lemon like fruit. People once carried citrine as protective talisman against the plague, bad skin and evil thoughts. It was also used as a charm against the bites of snakes and other venomous reptiles.
Opal is accepted for October birthdays and is the gemstone for 14th anniversaries. Sources are Australia, Mexico, and The USA.
There are more than a dozen varieties of fiery and iridescent opals. In fact, its tremendous color spectrum is the major reason for the opal’s mysterious attractiveness. The most popular have a white body color with flashes of many colors or “fires.”
Opal has symbolized hope, innocence and purity through the ages. In the Middle Ages, young fair-haired girls, wore opals in their hair to protect its lovely blond color. Medieval writers believed the opal could render its wearer invisible when the need arose. The ancient Romans believed the opal was the king of gems because it held within itself all the colors of rainbow.
Sapphire is the birthstone for September and the gemstone for 5th and 45th anniversaries. They are found in Sri Lanka, Australia, East Africa, and Southeast Asia.
Sapphire, a variety of corundum, comes in all colors except red, with the most popular being deep blue. Rare orange, pink and lavender varieties, along with rich velvety blue are the most expensive. Like ruby, its twin except for color, the sapphire is second only to the diamond hardness.
Some ancient writers claimed the Ten Commandments were written on sapphire. Ancient marriage partners had great faith in the stone, believing it would not shine if worn by wicked or impure. They were reported to be an excellent all-purpose medicine; and antidote against poison and having the power to stop bleeding and cure disorders of the eye. Sapphires were considered to be so powerful they continued to protect the original owner even after being sold.
Peridot is the birth stone for August and 16th anniversary gemstone, and mainly in Burma and the USA.
Peridot is sometimes referred to as an “Evening Emerald” because under artificial light the stone glows as a brilliant green. Choice peridot is transparent and its color varies yellow green to brilliant light green. Peridot is the child of volcanic action, crystals are sometimes combed from the black sands of Hawaii. It is abundant and available in larger sizes.
The peridot symbolize eloquence and persuasiveness; it was dedicated to St. Bartholomew. Treasured peridots found their way into cathedrals during the Crusades. Many legends state that peridot was considered a powerful amulet against all evil, as well as a remedy for sinus problems. It is said that if the gem was set in gold, it had the power to protect its wearer from terrors of the night, fears and bad dreams. Peridot were especially favored by pirates.
Rubies come from Burma, Thailand, Kenya, Tanzania, Cambodia, Sri Lanka, and India. It is the accepted gemstone for July birthdays, also 15th and 40th anniversary.
The ruby is named because of its rich red color. The ruby is a very durable gemstone; its hardness is surpassed only by diamond. Large rubies are very scarce and costly, worth more than 2 to 3 times a diamond of equal size and quality.
Rubies were thought to contain a glowing spark struck from the planet Mars. Ancient lore held that the ruby was capable of curing illness and reconciling lovers quarrels. Hindus referred to the ruby as “The Lord of the Gems,” and believed its deep red color came from an inextinguishable fire which was capable of boiling water. It is said that a person should never make faces at a ruby in a museum, and never ignore it, for it was said to grow dull if slighted or not worn or seen.
Pearl is the official birth stone of the month of June. It is also the accepted anniversary gemstone for the 3rd and 30th years of marriage.
A pearl is the product of an oyster’s defense mechanism. When a foreign irritant is introduced naturally or by man (cultured), the oyster immediately surrounds it with layers of a substance called nacre. This forms the exquisite gemstone known as pearl. Pearls come in a wide range of colors from delicate rose white to black. They should be relatively free from skin blemishes. The more perfectly round the shape the better. The higher the luster or “orient,” the more valuable the specimen. Besides the popular round shape, there are stylish mabe (large hemispherical cultured pearls), fresh water (elongated in interesting shapes and colors), and South Sea (large cultured pearls 10 mm and up from Australian and Indonesian waters), to name a few.
The oriental pearl is known as the gem of the moon. They have been recognized as the emblem of modesty, chastity, and purity. They have also come to symbolize a happy marriage.
Emerald is the birth stone for the month of May and is also the anniversary gemstone for 20th and 35th years of marriage. They are found mainly in Colombia, Brazil Zambia, and Zimbabwe.
The emerald is known as the Queen of Gems, and the gem of queens. The most prized is pure green or slightly bluish green. Emeralds are often characterized by the garden of included crystals trapped within. Under magnification, you will see all sorts of lovely patterns resembling foliage in a garden. A flawless, clear emerald is very rare and is usually found in small sizes. Small to medium sized stones are often faceted in the “step” or emerald cut. The gem is also lovely when cut into a Cabochon or dome shape. Sometimes emeralds are even carved.
The ancients held the emerald in great esteem, believing they sharpened the wearer’s eyesight and mind. The earliest engravers kept emeralds on their work tables to gaze upon from time to time to rest their tired eyes. Travelers relied on emeralds as protection against the hazards and perils of long journeys. The green gem was also said to give its owner the power to predict the future.
Diamond is the birth stone for month of April, and besides being the most popular gemstone for engagement rings, is the anniversary gem for the 10th and 60th years of marriage. Diamonds are found in Australia, Congo, Botswana, Russia, and South Africa.
Even though the diamond is the hardest of all gemstones known to man, it is the simplest in composition: it is common carbon. The ancient Greeks believed that diamonds were splinters of stars fallen to earth. It was even said by some that they were the tears of the Gods or perhaps crystallized lighting or hardened dew drops. The truth is, however, that the exact origin of diamonds is still something of a mystery, even to scientist and geologists.
In ancient times only kings wore diamonds as a symbol of strength, courage, and invincibility. Over the centuries, the diamond acquired its unique status as the ultimate gift of love. It was said that Cupid’s arrows were tipped with diamonds which have a magic that nothing else can ever quite equal. But it wasn’t until 1477, when Archduke Maximillian of Austria gave a diamond ring to Mary of Burgundy, that the tradition of engagement rings began. Even the reason a woman wears it on the third finger of her left hand dates back to the early Egyptian belief that the vena amoris, vein of love, ran directly from the heart to the top of the third finger, left hand.
Aquamarine is one of the traditional birthstone for March. It is also the anniversary gem for the 19th year of marriage. Aquamarine is found mainly in Brazil, Nigeria, and Zambia.
The ideal color of aquamarine is a refreshing sea blue. If you are looking for a big, durable gemstone, aqua is readily available in larger sizes and is truly dramatic when cut in rectangular or oval shapes. It is a member of the important beryl family, which also includes emerald.
Derived from the Latin meaning “sea water,” aquamarine was said to aid seafarers; thus it makes an excellent gift for sailors or those who travel frequently by sea. To dream of aquamarine signifies the making of new friends. To wear aquamarine brings love and affection. They are thought to give the wearers knowledge, foresight and assist in an individual’s inspiration. It is a universal symbol of youth, fidelity, hope, and health.
Amethyst is the birth stone for February and the anniversary gemstone for sixth year of marriage. It is found mainly in Brazil, Uruguay, Sri Lanka, the Ural Mountains of Russia, Madagascar, and Zambia.
Amethyst is a variety of quartz, ideally deep medium purple with rose colored flashes, however it ranges from pale lilac to nearly black purple shades.
The ancient Greeks believed that whoever wore an amethyst or drank from an amethyst chalice would not fall victim to intoxication. It is also said to have a sobering effect on those over excited by love’s passion. It has symbolized peace, protection and tranquility. Some say it will prevent baldness and improve complexion, while protecting from treason and deceit. Because royalty has always adored the color purple, amethysts abound in the ornaments of ancient Greeks and Egyptians, and in the British Crown Jewels.
Garnet is the birth stone for month of January and the anniversary gemstone for second year of marriage. Garnets are found in Brazil, Madagascar, Sri Lanka, India, Siberia, Africa, and the USA.
Nearly everyone thinks of garnet as a red gem. In fact, this family of gemstones is available in all colors except blue. Garnets offer enough variety in appearance to suite every taste.
There are many ancient traditions and legends about garnets. Some Hebrew writers include it as one of the 12 gems in Aaron’s breastplate. Christian tradition long considered the blood red garnet symbolic of Christ’s sacrifice. The Koran holds that it illuminates the Fourth Heaven of the Moslems. Garnet was said to give its guidance in the night allowing him to see when others couldn’t. Legend claims that Noah hung a large garnet in the ark for illumination. According to the Egyptians, garnet is an antidote for snake bite and food poisoning.
Zale Corp to close 60 stores in 90 days
Wants to cut annual capital spending from the planned $110 million to $85 millionGJF to spread its ‘trust mark’ nationwide
Will target 250 jewellery retailers in Phase ITiffany authorises repurchase
Investor also increases his stake; now owns 10.71 million Tiffany sharesDe Beers' lawsuit to be heard soon
Claimants say that De Beers was involved in unfair trade and promotionsDTC cocktail party ends on an ambitious note
Shine and Penny reiterate the growth plans of the DTCRio Tinto may reconsider investment in Zimbabwe
Awaits the implementation of the BillMacau Fair - a launch pad for China
Will allow global diamond companies to gain from the growing demand of China's marketsAstronomers discover largest diamond in galaxy
Lucy weighs 10 billion trillion trillion caratsDTC implements its BPP
Bans suplpies to six companies, two have lost sights for the current yearUS polished imports grew by 8.6% in value
Polished imports from india gre in value by 10.7%19th IJT-int'l Jewellery Tokyo
January 23, 2008 - January 26, 2008 |
Organiser: | IJT Show Management and Reed Exhibitions Japan Ltd. |
Venue: | Tokyo Big Sight, Japan, |
Phone: | +81-3-3349-8503 |
Fax: | +81-3-3345-7929 |
Email: | |
Website: | |
Description: | The 19th International Jewellery Tokyo (IJT 2008) will open its doors to its biggest show ever at Tokyo Big Sight in January. Already the largest trade show for jewellery and gemstones in Japan, IJT will continue its grand record of success by welcoming 1,500 exhibitors, the largest figure ever, from both Japan (900 exhibitors) and overseas (600 exhibitors). This is an increase of approximately 160 companies from the previous year. |
Added by: | Diamond World |
Jewelers International
Showcase (JIS)
January 19, 2008 - January 21, 2008 |
Organiser: | Jewelers International Showcase, Inc. |
Venue: | Miami Beach Convention Center, |
Phone: | +1-561-998 0205 |
Fax: | +1-561-998 0209 |
Email: | |
Website: | |
Description: | Jewelers International Showcase (JIS) now in its 29th year of serving the Jewelry Industry has become the largest Independent Jewelry Tradeshow in the Western Hemisphere. World-Wide Manufacturers and Wholesalers of Jewelry market and sell their products and services to the Jewelry Trade Attendees primarily from Florida, the Caribbean, Central and South America plus now many other USA States. All products and services exhibited at the JIS Shows must be within the profile of those purchased by Retail Jewelry Firms and Wholesalers of finished Jewelry. The product range at JIS Shows covers all price points from the highest Exotic Designer Lines and Trend Setters to everyday popular inventory items. Most items at the shows tend towards the middle and higher price points but there is something for every trade member’s inventory including competitively priced jewelry as well. |
Added by: | Diamond World |
MACEF Milano
January 18, 2008 - January 21, 2008 |
Organiser: | Fiera Milano International S.p.A. |
Venue: | Fiera Mialno International Milan, Italy, |
Phone: | +39 0248550.1 |
Fax: | + 39 0248550.800 |
Email: | |
Website: | |
Description: | Macef, the International Home Show, an exhibition dedicated to table and kitchenware (articles for the table and products for the kitchen); furnishing and decoration (furnishing accessories, decorations, textiles and design objects); classic (classic furnishing accessories, bomboniere and silver objects for the home), gifts (fancy goods, gift articles and stationery); bijoux, gold and accessories (gold and costume jewellery, accessories). It is the city's main exhibiting event on an annual basis, by number of exhibitors and by covered surface and represents and has been offering one of the most comprehensive overviews of the relevant sectors for over 40 years. |
Added by: | Diamond World |
The Macau Jewellery & Watch Fair
January 10, 2008 - January 13, 2008 |
Organiser: | CMP Asia Ltd |
Venue: | The Cotai Strip ™ Convention and Exhibition Center at The Venetian, |
Phone: | (852) 2516 1636/1677 |
Fax: | (852) 2802 9934 |
Email: | |
Website: | |
Description: | The Macau Jewellery & Watch Fair (1MJ) is Asia's first and only international trade fair for the jewellery and watch industry at the beginning of the year. Certain to be a major new marketplace for all sectors of the worldwide jewellery industry, the Fair is expected to attract over 300 exhibitors from all over the world to exhibit a wide range of jewellery products of the highest quality, including fine jewellery, gemstones, pearls, diamonds, antique & estate jewellery and related products and services. |
Added by: | Diamond World |
International Gem & Jewelry Show Inc.
January 11, 2008 - January 13, 2008 |
Organiser: | International Gem & Jewelry Show, Inc. |
Venue: | Broward County Convention Center, Ft. Lauderdale, |
Phone: | (301) 294-1640 |
Fax: | (301) 294-0034 |
Email: | |
Website: | |
Description: | The International Gem & Jewelry Shows have two sections: one section open to the public and another open to members of the trade. At these shows you will find thousands of quality dealers in every type of jewelry imaginable. From one-of-a-kind creations and estate jewelry to celebrity exhibits and accessories, we offer products for everyone from the rock hound to the amateur jeweler. This selection combined with prices well below retail attracts visitors to our shows from every corner of the world. |
Added by: | Diamond World |
Notes On Specific Gravity
Copyright © Charles Lewton-Brain 1986 - 1994
Archimedes is said to have discovered that when a body is placed in water the volume of water displaced is equal to the volume of the body and that when the body is placed in water that it undergoes an apparent loss of weight. This loss of weight is equal to the weight of the water displaced. When a gem is weighed in air and then weighed in water the loss of weight is equal to the weight of its volume in water displaced. The weight of the gem in air divided by the loss of weight in water gives the specific gravity of the stone or material.
Specific gravity is then defined as "The weight of a body compared with the weight of an equal amount of pure water at 4oC (4oC is essentially the temperature at which water is densest). In practice room temperature water is used. What this means is that a given volume of ruby weights 4 times as much as an equal volume of water or a given volume of diamond weighs 3.52 times as much as an equal volume of water. An example of using this is: gem weighs 5 ct in air, loss of weight is 1.25 ct. in water (weight units do not matter, grams, carats).
Calculate:
The gem is then corundum with an SG of 4.00 (3.99).
The specific gravity for each mineral is the same within narrow limits (except in species like topaz or garnet and zircon where subgroups with definite specific gravities occur). If one can determine the specific gravity of a gem one can usually identify it. In practice however because of time constraints and other factors specific gravity determination is usually used as a corroborative test or for large, rough or carved samples.
There are a number of SG balances made for measuring specific gravity. These allow the SG of the sample to be read directly from their scales. Two are the Westphal and the Hanneman. The Hanneman balance is extremely inexpensive ($10.00 US), fairly fast and easy to use. It is very accurate and can give accurate results on stones as small as .5 ct with care while other balances are not accurate below 3.0 cts. There are 5 cts to the gram.
A regular diamond or chemical balance, mechanical or electronic may be adapted for hydrostatic SG determinations by devising a way of weighing the stone in air, then in water, using the same pan. The conditions required are:
1. A bridge is constructed for the left hand side of the balance. This sits above the pan without touching or otherwise interfering with the operation of the balance at any time in its use. The bridge should not be magnetized.
2. A beaker of water (distilled, deionized, degassed) is placed on the bridge. A tiny drop of wetting agent, alcohol, or better photo-flo or dishwashing liquid is added to the water to decrease surface tension which can adversely affect the results. This too may not hinder or touch the operation of the balance.
3. An extremely thin lightweight metal spiral wire 'cage' is constructed which hangs from the left hand side of the balance arm. The spiral 'cage' is submerged in water. It should be of rustproof metal like brass, copper, stainless steel, titanium or tungsten.
4. A counterbalance wire is hung from the opposite side of the balance arm at the same position. This is cut so as to balance the 'cage' wire as completely as possible
diamond or chemical balance accurate to 3 decimal places (.001g)
Procedure to Determine SG of a Gemstone Over 3 ct
1. Zero the balance. If your counterbalance wire does not do this you have to add some weights to the right hand pan (for right handed people) to get the indicator needle of the balance to register zero or perfect balance. This weight must of course then be subtracted from your later additions of weights to this pan.
2. Clean the stone very carefully with a gem cloth. If it has wax or grease on it this must be removed. Use alcohol and wipe clean. Examine it for large flaws or inclusions which might affect the accuracy of the results.
3. Place it on the left hand pan underneath the bridge and weight the stone. Record the result. Weighings are done to three decimal places.
4. Place the stone in the spiral cage and weigh it in water. Record the result. Brush off any bubbles on the stone or wire with a fine brush.
5. Subtract the second result from the first to find the difference. (The loss of weight in water).
6. Calculate:
7. For more accurate results repeat the procedure at least three times and average the results. Make sure the stone is dry before repeating the air weighing.
With an electronic balance the procedure is similar except that only one balance pan is used. As you will not be able to zero the balance the weight of the spiral cage suspended in water is the zero weight and all calculations are done from this reference point. eg. if it weighs .3 grams then subtract .3 grams from all calculations.
There are several other methods of determining specific gravity hydrostatically. For large specimens a spring balance and a bucket of water may be used. The larger the object the more accurate the results.
Other Balance Methods
(Sinkakas, Gemstone and Mineral Databook, pp 123 -126)
For large samples, sculptures, rough.
1. Weigh specimen in grams.
2. Partly fill a graduated cylinder (cc) with water.
3. Drop in sample, note new volume.
4. Difference between volumes = volume of water displaced in grams.
5. Calculate:
This method is rough.
Also: 1. Weigh specimen.
2. Place a beaker partly filled with water on balance and weigh.
3. Leaving beaker and water in place submerge the sample with a very thin thread or nylon monofilament in the water.
4. The beaker and water gain weight, rebalance and note new reading.
5. The difference between new weight and earlier weight is the weight of the water displaced by the sample. This too is a rough method.
Causes of Error in Hydrostatic SG Determination
1. Too small a specimen.
2. Surface tension of water. One drop of detergent liquid the size of a pin head destroys surface tension in 1 liter of water.
3. Failure to degas water. Use boiled, deionized water that has been sitting for a time.
4. Failure to record and compensate for temperature corrections when using liquids other than water.
5. Failure to multiply SG by density of liquid other than water.
To avoid problems of surface tension other liquids than water may be used. Examples are Carbon Tetrachloride, toluene and alcohol. Ethylene dibromide was used but is now considered too dangerous. Recommended is toluene or alcohol. Because temperature affects the SG of these liquids one must refer to the literature for each temperature change when using them. In practice it may be better to find the exact SG of the liquid you are using at the time of use and then refer to your SG and temperature correlations as you build them up with time. Such liquids are used for small stones to increase accuracy. To find the SG of a liquid use a very clean piece of quartz which has a constant SG of 2.651 (a gemstone and weigh as if to obtain the SG. Then solve the equation:
Heavy Liquid Methods
Various liquids and chemicals have a wide range of SGs. When a stone is placed in a liquid of the same SG it suspends, and stays where it was placed (or sinks or rises very slowly). If it has a lower SG (is 'lighter') than the liquid it floats. If it is denser (has a higher SG, is 'heavier') it sinks. Therefore, given a range of liquids of known SGs it is possible to estimate or even determine the SG of a stone by its behavior in the liquids.
Heavy liquids should not be used at all without a properly tested fume hood. Cleanliness and proper working methods are essential because they can cause severe health damage and can be absorbed through the skin and by breathing. They belong in a properly equipped gemmolocial laboratory.
The Advantages of Heavy Liquids Include:
1. Speed. It is very fast. One usually begins with the densest liquid and goes to the next less dense until the stone sinks to the bottom. If you are lucky it suspends.
2. One can use them for stones under 3 ct. Stone size makes no difference.
3. As an ancillary method it may be very rapid to check or corroborate other tests.
4. Very quick for separating different types of similar appearing stones from the same package. For example checking beryl (emerald) one might make up a liquid with the density of 2.71 (Indicator is calcite).
Disadvantages:
1. The liquids used are really toxic, hazardous to your health, messy, smelly, poisonous and in some cases corrosive.
2. Cracked, flawed stones may give inaccurate readings.
3. Stones must be unmounted.
4. Porous stones may not be tested (opal, turquoise, organic gemstones).
5. The liquids attack many plastics.
There are three liquids recommended by gemology text books for general use.
Bromoform SG 2.88
Methylene Iodide SG 3.33
Monobromonapthalene SG 1.49 This is used to dilute and lower the SGs of the other two. Liddicoat suggests the use of toluene which is very flammable and evaporates faster than monobromonapthalene but is cheaper.
Liquid Number | Indicator | ||
#1 | 2.65 SG | Bromoform diluted with monobromonapthalene. Quartz, feldspars, iolite float, most other stones sink. | Quartz |
#2 | 2.88 SG | Bromoform, undiluted. Beryl floats, other green blue stones sink. | |
#3 | 3.05 SG | Methylene iodide diluted with monobromonap- Tourmaline thalene. Tourmaline floats, nephrite floats, jadeite sinks. | |
#4 | 3.33 SG | Methylene iodide undiluted. Jadeite, peridot suspend or float or sink very slowly, topaz sinks, tourmaline floats, etc. |
There are also solutions made up with an SG of 3.52 (diamond indicator) and 4.00 (corundum indicator) using a liquid called Clerici solution which may be diluted with water.
Indicators of clear gemstones may be used as a check on the liquid SG before use as evaporation etc. can change the SG. Manufactured glass SG indicators in a wide range are also available. It should be noted that relative speed of sinking is a good indication of SG range. If a stone sinks very rapidly then it is a lot denser than the liquid, slowly it is similar. The degree to which it floats on a liquid can also tell something about its SG. High floating means it is a lot less dense, low floating similar, suspends - the same. Make sure to tap or dunk a stone with tweezers to ensure that surface tension is not holding it up.
Although Clerici solution offers many advantages to the gem tester it is no longer recommended as it is extremely toxic, corrosive and recently shown to be carcinogenic. It demonstrates an exact correlation between SG and RI as it is diluted. It may be diluted until a gemstone suspends and then a drop of it placed on a refractometer and the RI found. The one looks at a straight line graph and reads off the SG of the solution and the stone. To reconcentrate it water is simply allowed to evaporate. At full concentration its SG is 4.28. The less toxic liquids can also be used in the same way to obtain a correlation between SG and RI. However they are not easy to reconcentrate. There are also other methods of obtaining the SG of a stone using heavy liquids.
Using Heavy Liquids
1. Adequate ventilation is necessary.
2. All tweezers, stones, etc. in contact with the liquids must be very carefully cleaned; perhaps with toluene as a solvent; between liquids to prevent contamination or corrosion of tools. Clean them extra carefully after finishing.
3. They are poison. No food, smoking or drinking is allowed when using heavy liquids.
4. Hands must be washed right after use whether or not they were in contact with the liquids.
The Hanneman Balance
1. Set up balance as described.
2. Clean the stone, check for flaws.
3. Slide zero weight to a position where the indicator needle registers zero on the zero card. If necessary adjust the zero card slightly. The balance should be as horizontal as possible.
4. Place stone in top left hand pan. Place indicator weight wires on the notch at the right of the balance until the needle registers zero again.
5. Place the stone carefully in the lower pan under water. Brush off any air bubbles. The needle will rise as the weight is less.
6. Slide the indicator weights wire to the left on the scale until the needle registers zero again.
7. Read the SG value (top scale). Repeat twice more and average for increased accuracy.
You can order the Hanneman balance and other items from: Hanneman Gemological Instruments, PO box 942L, Poulsbo, WA, 98370, USA
Basic Optics Notes for Gemology
Copyright © Charles Lewton-Brain 1986 -1994
The optical characteristics and properties of gemstones often provide the fastest and best methods of identification. A certain amount of theory is necessary as optical principles determine cutting methods, gemstone attributes and the function of gem testing instruments.
Light
Light and our perception of it play a crucial role in our appreciation of and identification of gemstones. Visible light however comprises only a small part of what is referred to as the electromagnetic spectrum.
While the wave or undulatory theory of light has been mostly superseded by the quantum (particle) theory the wave theory best serves the purpose of describing light for gemmology. We can consider the electromagnetic spectrum to consist of an infinite number of types of wavelengths, from short to very long. Different wavelengths have different powers of penetration dependent upon their length relative to the medium they pass through. X-rays for example with a wavelength near atomic sizes pass through or between most atoms. The amount passed depends upon the mass of the atom concerned. Dense atoms like lead for instance provide a screen against x-rays. An application of this is a test for diamonds, whether set or unset, where the suspect stones are x-rayed for ten seconds over photographic paper. Carbon atoms are small (low mass) and so diamond is transparent to x-rays and is invisible on the photograph while all diamond simulants show up as positive, opaque shapes.
A rough wavelength scale follows:
White light is composed of a mixture of a great many wavelengths each of which is perceived as a different colour. The wavelength of violet light for example is about half that of red light. The wavelengths of white light may be divided into:
Red 700.0 nm to 640.0 nm
Orange 640.0 nm to 595.0 nm
Yellow 595.0 nm to 575.0 nm
Green 575.0 nm to 500.0 nm
Blue 500.0 nm to 440.0 nm
Violet 440.0 nm to 400.0 nm
Transparency Refers to the ease with which light is transmitted through a substance. Classifications of transparency in cut gemstones include:
1. Transparent stones. An object viewed through the gem shows outlines clearly and distinctly (diamond, topaz, corundum).
2. Semi-transparent. Blurred outlines of object but a great deal of light still passes through the stone, i.e. chalcedony.
3. Translucent. Some light passes through, no object can be seen through stone, i.e. opal, some jades, much cryptocrystalline quartz.
4. Semi-translucent. Light is only transmitted through edges, where they are thin, i.e. turquoise.
5. Opaque. No light passes through, i.e. malachite, pyrites.
Colour and degree of colour will affect transparency as will inclusions, flaws, etc. Quality will also affect it. The characteristics are subjective in nature and overlap exists.
Reflection of Light
If a ray of light falls onto a plane mirror the light is reflected away from the surface. The angle of incidence NOI equals the angle of reflection NOR and IO, NO and RO are in the same plane. All angles in optics are measured from the 'normal', an imaginary line at right angles to the surface at the point of incidence (where the light ray strikes the surface).
Refraction
A ray light entering an optically denser medium is bent (refracted) towards the normal. The greater the bending (refraction) for a given angle of incidence the greater is the refractive power of the stone.
The cause of refraction is that the light waves (300,000 km/second) are slowed down as they enter the optically denser medium. In the 17th century Snell (Dutch scientist) described laws relating angles of incidence and refraction for two media. There is a constant ratio between the sines of these angles for any given two media. The constant ratio obtained is called the refractive index. Air is chosen as the rarer medium and yellow sodium light is the standard for refractive index measurements. Refractive index is a measure of a gem's refractive power. It is the ratio of the sine of the angle of incidence divided by the sine of the angle of refraction when light passes from air into the denser medium.
Gems refractive indices range from under 1.5 to over 2.8.
Total Internal Reflection
A ray passing in the opposite direction, from the denser to the rarer (gem to air) medium is bent (refracted) away from the normal.
As the angle of incidence is increased the angle of refraction away from the normal increases until a point is reached when the ray I1OR1 exits parallel to the table of the stone. Any further increase in this angle causes the ray to be totally reflected back into the gem. Ray I2OR2 has been reflected back into the gemstone. This is called total internal reflection and the angle I1OM is called the critical angle for the medium in question. The brilliant cut of diamonds uses total internal reflection and the critical angle for diamond and air to ensure that all light entering the stone is totally reflected and passes out the table or crown facets of the stone. The critical angle is also what enables a refractometer to differentiate gemstones of different species.
Dispersion
A white light ray entering an optically denser medium and leaving by a plane inclined to that of entry will have its colours separated, analyzed, spread out. This is because each colour has a different wavelength and so is differently slowed down (refracted) by the medium. Red (longest wavelength) is slowed the least and violet (shortest wavelength) the most.
This spreading is termed dispersion. In gemstones the effect gives rise to the stone's 'fire'. It may be measured with complex equipment and numerical values given. The higher the number the greater the fire where the stone's colour does not mask the effect, as in demantoid (green) garnet with a greater dispersion (.057) than diamond (.044). With practice and standard stones numerical estimates of dispersion may be made with the Hanneman/Hodgkinson slit technique.
Plane Polarized Light
When a light ray passes through a doubly refractive gemstone it is split into two rays with different amounts of refraction. Each ray is plane polarized, that is instead of the wave vibrating all directions about the line of the ray it vibrates in a single plane only. Each ray is plane polarized at right angles to the other. As each ray is differently refracted so it is differently absorbed by the stone and possesses in coloured gems a different hue or colour.
The Dichroscope picks up each ray at the same time and allows one to view them side by side. A simple dichroscope is a block of calcite with black paper glued to one end which has a small rectangular hole cut in it. The viewer sees two images because the light ray has been split by the high double refraction of calcite. Each image is of a different ray (each ray is also plane polarized at right angles to the other - this is what allows the calcite to present them separately). If a difference in colour exists it will be visible by comparison. One must always test in several directions. This can be of some use in identifying gemstones by their characteristic dichroic or trichroic colours but is usually used as a method of detecting double refraction. Presence of dichroism proves double refraction. Absence does not mean a material is not doubly refractive - it may be that the dichroism is very weak, or in transparent stones there is none evident. It can be used to find an optic axis. If three colours (trichroic) are seen it means the stone is biaxial. If two only are seen it is uniaxial. Transmitted, not reflected light must be used as reflected light may be partly polarized. Most natural corundum is cut with the table oriented to the optic axis and will show no dichroism through the table. Most synthetic corundum has the table parallel to the optic axis and dichroism is strongest through the table. This is then an indication of synthetic origin.