Monday, May 4, 2009
Sunday, May 3, 2009
Gold is Gold
Gold is a soft, very dense metal which is highly valued for use in jewelry and coinage. Called a "noble metal", it does not react readily in ordinary chemical reactions, so it can be found in essentially pure form as gold nuggets. It is also used in dental work because it can be precisely shaped and does not react chemically in the mouth. Its high electrical conductivity makes it valuable for tiny electrical contacts, and its very high reflectivity has led to use in thin films as a reflector.
Gold is bright yellow by reflected light, but in thin films may be blue or green.
Gold is the most malleable and the most ductile of all metals. It can be hammered into sheets only 1/100,000 cm thick and drawn into wires 1/5000 cm in diameter.
Gold is often alloyed with copper, silver, palladium or other metals. The amount of gold in these alloys is described in carats. The carat value is the number of parts of gold in 24 parts of alloy, so that 24 carat gold is the pure metal. American coinage gold is 21.6 carat and British coinage is 22 carat.
White gold as used in jewelry is usually an alloy of gold and nickel.
Gold is found in the mineral nagyagite, a sulfide, along with lead, iron, antimony, and tellurium. Tellurium combines with gold to form krennerite, AuTe2.
Gold is bright yellow by reflected light, but in thin films may be blue or green.
Gold is the most malleable and the most ductile of all metals. It can be hammered into sheets only 1/100,000 cm thick and drawn into wires 1/5000 cm in diameter.
Gold is often alloyed with copper, silver, palladium or other metals. The amount of gold in these alloys is described in carats. The carat value is the number of parts of gold in 24 parts of alloy, so that 24 carat gold is the pure metal. American coinage gold is 21.6 carat and British coinage is 22 carat.
White gold as used in jewelry is usually an alloy of gold and nickel.
Gold is found in the mineral nagyagite, a sulfide, along with lead, iron, antimony, and tellurium. Tellurium combines with gold to form krennerite, AuTe2.
Saturday, May 2, 2009
How Pearls are Formed and Their Various Types?
There are essentially three types of pearls: natural, cultured and imitation. A natural pearl (often called an Oriental pearl) forms when an irritant, such as a piece of sand, works its way into a particular species of oyster, mussel, or clam. As a defense mechanism, the mollusk secretes a fluid to coat the irritant. Layer upon layer of this coating is deposited on the irritant until a lustrous pearl is formed.
A cultured pearl undergoes the same process. The only difference is that the irritant is a surgically implanted bead or piece of shell called Mother of Pearl. Often, these shells are ground oyster shells that are worth significant amounts of money in their own right as irritant-catalysts for quality pearls. The resulting core is, therefore, much larger than in a natural pearl. Yet, as long as there are enough layers of nacre (the secreted fluid covering the irritant) to result in a beautiful, gem-quality pearl, the size of the nucleus is of no consequence to beauty or durability.
Pearls can come from either salt or freshwater sources. Typically, saltwater pearls tend to be higher quality, although there are several types of freshwater pearls that are considered high in quality as well. Freshwater pearls tend to be very irregular in shape, with a puffed rice appearance the most prevalent. Nevertheless, it is each individual pearls merits that determines value more than the source of the pearl.
Regardless of the method used to acquire a pearl, the process usually takes several years. Mussels must reach a mature age, which can take up to 3 years, and then be implanted or naturally receive an irritant. Once the irritant is in place, it can take up to another 3 years for the pearl to reach its full size. Often, the irritant may be rejected, the pearl will be terrifically misshapen, or the oyster may simply die from disease or countless other complications. By the end of a 5 to 10 year cycle, only 50% of the oysters will have survived. And of the pearls produced, only approximately 5% are of substantial quality for top jewelry makers. From the outset, a pearl farmer can figure on spending over $100 for every oyster that is farmed, of which many will produce nothing or die.
Imitation pearls are a different story altogether. In most cases, a glass bead is dipped into a solution made from fish scales. This coating is thin and may eventually wear off. One can usually tell an imitation by biting on it. Fake pearls glide across your teeth, while the layers of nacre on real pearls feel gritty. The Island of Mallorca is known for its imitation pearl industry.
A cultured pearl undergoes the same process. The only difference is that the irritant is a surgically implanted bead or piece of shell called Mother of Pearl. Often, these shells are ground oyster shells that are worth significant amounts of money in their own right as irritant-catalysts for quality pearls. The resulting core is, therefore, much larger than in a natural pearl. Yet, as long as there are enough layers of nacre (the secreted fluid covering the irritant) to result in a beautiful, gem-quality pearl, the size of the nucleus is of no consequence to beauty or durability.
Pearls can come from either salt or freshwater sources. Typically, saltwater pearls tend to be higher quality, although there are several types of freshwater pearls that are considered high in quality as well. Freshwater pearls tend to be very irregular in shape, with a puffed rice appearance the most prevalent. Nevertheless, it is each individual pearls merits that determines value more than the source of the pearl.
Regardless of the method used to acquire a pearl, the process usually takes several years. Mussels must reach a mature age, which can take up to 3 years, and then be implanted or naturally receive an irritant. Once the irritant is in place, it can take up to another 3 years for the pearl to reach its full size. Often, the irritant may be rejected, the pearl will be terrifically misshapen, or the oyster may simply die from disease or countless other complications. By the end of a 5 to 10 year cycle, only 50% of the oysters will have survived. And of the pearls produced, only approximately 5% are of substantial quality for top jewelry makers. From the outset, a pearl farmer can figure on spending over $100 for every oyster that is farmed, of which many will produce nothing or die.
Imitation pearls are a different story altogether. In most cases, a glass bead is dipped into a solution made from fish scales. This coating is thin and may eventually wear off. One can usually tell an imitation by biting on it. Fake pearls glide across your teeth, while the layers of nacre on real pearls feel gritty. The Island of Mallorca is known for its imitation pearl industry.
Friday, May 1, 2009
Where Pearls are Found?
Historically, the world's best pearls came from the Persian Gulf, especially around what is now Bahrain. The pearls of the Persian Gulf were natural created and collected by breath-hold divers. The secret to the special luster of Gulf pearls probably derived from the unique mixture of sweet and salt water around the island. Unfortunately, The natural pearl industry of the Persian Gulf ended abruptly in the early 1930's with the discovery of large deposits of oil. Those who once dove for pearls sought prosperity in the economic boom ushered in by the oil industry. The water pollution resulting from spilled oil and indiscriminate over-fishing of oysters essentially ruined the once pristine pearl producing waters of the Gulf. Today, pearl diving is practiced only as a hobby. Still, Bahrain remains one of the foremost trading centers for high quality pearls. In fact, cultured pearls are banned from the Bahrain pearl market, in an effort to preserve the location's heritage.
The largest stock of natural pearls probably resides in India. Ironically, much of India’s stock of natural pearls came originally from Bahrain. Unlike Bahrain, which has essentially lost its pearl resource, traditional pearl fishing is still practiced on a small scale in India.
The art of culturing pearls was invented in Japan in 1893 by a man named Kokichi Mikimoto. He discovered that by introducing a tiny bead of mother-of-pearl (the white substance on the inside of a mussel’s shell) into an oyster, that oyster would began to cover the irritant with nacre (the secreted substance that makes up a pearl). To this day, the Japanese are considered the foremost experts in seeding oysters and the Mikimoto family continues to be one of the largest pearl producing empires.
Interestingly, one of the first places to begin farming cultured pearls outside of Japan was near the Gulf of California in Mexico. Unfortunately, Mexican pearls disappeared from the international markets when overfishing of natural pearl oyster banks took its toll and the Mexican government had to impose a No- Fishing law in the late 1940's. Mexico is today attempting to return to the pearl market with cultured half-pearls (meaning they are only pearl slices or hemispheres, not round).
Pearls predominately come from Japan, Australia, Indonesia, Myanmar, China, India, Philippines, and Tahiti. Japan however, controls roughly 80% of the world pearl market, with Australia and China coming in second and third, respectively. The South Sea waters around Australia, Indonesia, and Myanmar are renowned for their large, white pearls, while Japan’s pearls are highly valued for their lustrous character. Freshwater pearls constitute the bulk of China’s pearl efforts. And as mentioned earlier, India is recognized as one of the last producers and handlers of naturally occurring pearls. Interestingly, although Australia’s pearls derive from the same sea as those from Indonesia and Myanmar, Australia consistently advertises their pearls as distinctly superior to other South Sea pearls, emphasizing the importance of the country of origin, not simply the body of water from which they came.
The largest stock of natural pearls probably resides in India. Ironically, much of India’s stock of natural pearls came originally from Bahrain. Unlike Bahrain, which has essentially lost its pearl resource, traditional pearl fishing is still practiced on a small scale in India.
The art of culturing pearls was invented in Japan in 1893 by a man named Kokichi Mikimoto. He discovered that by introducing a tiny bead of mother-of-pearl (the white substance on the inside of a mussel’s shell) into an oyster, that oyster would began to cover the irritant with nacre (the secreted substance that makes up a pearl). To this day, the Japanese are considered the foremost experts in seeding oysters and the Mikimoto family continues to be one of the largest pearl producing empires.
Interestingly, one of the first places to begin farming cultured pearls outside of Japan was near the Gulf of California in Mexico. Unfortunately, Mexican pearls disappeared from the international markets when overfishing of natural pearl oyster banks took its toll and the Mexican government had to impose a No- Fishing law in the late 1940's. Mexico is today attempting to return to the pearl market with cultured half-pearls (meaning they are only pearl slices or hemispheres, not round).
Pearls predominately come from Japan, Australia, Indonesia, Myanmar, China, India, Philippines, and Tahiti. Japan however, controls roughly 80% of the world pearl market, with Australia and China coming in second and third, respectively. The South Sea waters around Australia, Indonesia, and Myanmar are renowned for their large, white pearls, while Japan’s pearls are highly valued for their lustrous character. Freshwater pearls constitute the bulk of China’s pearl efforts. And as mentioned earlier, India is recognized as one of the last producers and handlers of naturally occurring pearls. Interestingly, although Australia’s pearls derive from the same sea as those from Indonesia and Myanmar, Australia consistently advertises their pearls as distinctly superior to other South Sea pearls, emphasizing the importance of the country of origin, not simply the body of water from which they came.
Thursday, April 30, 2009
What are Kimberlites?
Unlike most of the surface rocks in Kansas, which are sedimentary in origin, kimberlite is an igneous rock, formed from the cooling of molten magma. Igneous rocks are extremely rare in Kansas. Kimberlite is composed of at least 35% olivine, together with other minerals such as mica, serpentine, and calcite (Jackson, 1997). Geologists call it an ultrabasic rock, which means it does not contain any quartz or feldspar, the two most common rock-forming minerals. Olivine, the main mineral constituent of the rock, is an olive-green, grayish green, or brown mineral made up of magnesium, iron, and silica. In 1888, the name kimberlite was proposed for this particular rock, based upon the occurrence of these rocks in the vicinity of Kimberley, South Africa.
Large volumes of an olivine-rich rock type called peridotite occur at great depths in the earth in a layer called the mantle. At these depths (100-135 miles or 150-200 km), the combined temperature and pressure is high enough to partially melt some of the peridotite. If volatile gases, such as carbon dioxide and water, are present, they may propel the molten peridotite upwards, forming a kimberlite magma. As the hot kimberlite magma rises slowly upward into regions of lower temperature and pressure in the upper mantle and overlying crust, minerals start to crystallize and the volatile gases expand and exert increasingly higher pressures on the surrounding rocks, eventually breaking some of the surrounding rock and incorporating it into the magma. Closer to the earth's surface the internal pressures of the magma and volatile gases become so great that the kimberlite becomes explosive. Kimberlite magma can rise toward the surface at speeds estimated at up to 400 meters (1,200 feet) per second, ripping up more and more pieces from the surrounding rock, which gives the kimberlite its characteristic texture.
Wednesday, April 29, 2009
Remarkable Facts of Diamonds
All diamonds are at least 990,000,000 years old.
Many are 3,200,000,000 years old (3.2 billion years)!!!
How do we know this?
Age: from Carbon dating? NO! C-dating only works for very young carbon. You need to use other radioactive decay schemes (e.g., uranium-lead) to date inclusions in diamonds. Inclusions used for dating are around 100 microns in diameter (0.1 mm).
Diamonds are formed deep within the Earth: between 100 km and 200 km below the surface.
Diamonds form under remarkable conditions!
* Diamond is made of carbon (C), yet the stable form (polymorph) of carbon at the Earth's surface is graphite.
* To ensure they are not converted to graphite, diamonds must be transported extremely rapidly to the Earth's surface.
Diamond is the hardest material.
* Diamonds are found in many localities, both overseas and in the US.
Many are 3,200,000,000 years old (3.2 billion years)!!!
How do we know this?
Age: from Carbon dating? NO! C-dating only works for very young carbon. You need to use other radioactive decay schemes (e.g., uranium-lead) to date inclusions in diamonds. Inclusions used for dating are around 100 microns in diameter (0.1 mm).
Diamonds are formed deep within the Earth: between 100 km and 200 km below the surface.
Diamonds form under remarkable conditions!
- The temperatures are about 900 - 1300 C in the part of the Earth's mantle where diamonds form.
- The pressure is between 45 - 60 kilobars. (kB)
Diamonds are carried to the surface by volcanic eruptions.
- + 50 kB = 150 km = 90 miles below the surface
- + 60 kB = 200 km = 120 miles below the surface
- The volcanic magma conduit is known as a kimberlite pipe or diamond pipe.
We find diamonds as inclusions in the (rather ordinary looking) volcanic rock known as kimberlite. - NOTE: The kimberlite magmas that carry diamonds to the surface are often much younger than the diamonds they transport (the kimberlite magma simply acts as a conveyer belt!).
* Diamond is made of carbon (C), yet the stable form (polymorph) of carbon at the Earth's surface is graphite.
* To ensure they are not converted to graphite, diamonds must be transported extremely rapidly to the Earth's surface.
- It is probable that kimberlite lavas carrying diamonds erupt at between 10 and 30 km/hour (Eggler, 1989). Within the last few kilometers, the eruption velocity probably increases to several hundred km/hr.
Diamond is the hardest material.
- Diamond is the hardest gem on the MOHS harness scale and graphite (also made from carbon atoms) is the softest! Given that both diamond and graphite are made of carbon, this may seem surprising.
- The explanation is found in the fact that in diamond the carbon atoms are linked together into a three-dimensional network whereas in graphite, the carbon atoms are linked into sheets with very little to hold the sheets together (thus the sheets slide past each other easily, making a very soft material).
* Diamonds are found in many localities, both overseas and in the US.
Tuesday, April 28, 2009
How to Buy a Diamond?
People mark special events with sentimental gifts of jewelry. While weddings reign as the biggest diamond event, there are many small yet glorious celebrations that are honored with beautiful sparklies, too, such as new jobs, anniversaries, graduations, births…the list, happily, is endless.
So how do people learn about diamonds so they can buy, own and enjoy them with confidence? The nonprofit Gemological Institute of America (GIA), the world’s foremost authority in gems and jewelry and the creator of the famous 4Cs of diamonds offers these five tips:
Choose a qualified jeweler.
- Select a jeweler as you would a doctor, a lawyer or any professional. Ask around. Find someone who is a trained gemologist, a GIA Graduate Gemologist or GIA Accredited Jewelry Professional, and is affiliated with a professional jewelry association.
- GIA’s Web site offers in-depth information on diamonds, pearls and other gemstones. GIA even built a special Web site on the Four Cs. Knowing the Four Cs helps you speak the language of diamonds and communicate with jewelers.
- All diamonds are rare and no two diamonds are alike. A diamond’s quality and rarity is determined by its unique combination of characteristics of Color, Cut, Clarity and Carat Weight. The International Diamond Grading System, used around the world since its invention by GIA in the 1950s, is based on the 4Cs.
- Carat: Diamonds are weighed in metric carats. Two carats weight about the same as a small paper clip. A carat is divided into 100 “points”, so a diamond of 50 points weighs 0.50 carats.
- Clarity: Nearly all diamonds contain unique clarity characteristics. Flawless diamonds are exceptional and costly. Most inclusions are invisible unless magnified.
- Color: Colorless diamonds are extremely uncommon. Most diamonds have a slight yellow or brown tint. GIA uses letters to represent colors, beginning with D (colorless) and ending at Z (light yellow or brown). “Fancy colored diamonds” come in every color imaginable, are also very unusual and have their own GIA color grading system.
- Cut: While diamonds come in different shapes, such as round, pear or marquise, the term “cut” refers to proportion. The well-cut, balanced diamond has unbridled brilliance, sparkle and fire.
- A diamond grading report tells you the exact gemological quality of your diamond. Is it a natural diamond? Is it a synthetic diamond? Has it been treated and how? What are its quality ratings according to the Four Cs?
- A diamond grading report describes the precise gemological quality of your diamond while an appraiser puts a monetary value to the stone. You can laser inscribe a personal message or the diamond’s unique GIA Grading Report number on the diamond’s girdle.
So, relax, do a little research, and before you know it you'll be as brilliant as diamond when it comes to diamond shopping.
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