Thursday, April 30, 2009
Wednesday, April 29, 2009
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
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.
Monday, April 27, 2009
It is important to distinguish where gems are formed from where they are found.
Almost all gems are formed below the Earth's surface.
- Some are brought to the surface through mining
- Some are brought to the surface through earth processes (faulting, folding, large scale uplift, volcanism). These processes can move rock up from more than 400 km below the surface.
- Water near Earth's surface
- Hydrothermal deposits
- Magmatic gems
- Metamorphic gems
- Gems of the mantle
Gems of the Mantle
Sunday, April 26, 2009
Internationally, the Institute has distinguished itself as the preeminent source of gemological knowledge and professionalism. The GIA Diamond Grading Report and the GIA Diamond Dossier® are considered to be the world's premier credentials of diamond quality. Many retailers provide diamond certification, however no report is as unbiased and complete as a GIA diamond grading report. Diamonds of all shapes and sizes are sent to the Institute from every corner of the globe for diamond grading and analysis.
Some famous diamonds have been graded by GIA including the Hope Diamond (45.52 carats), the Steinmetz Pink (59.60 carats), the Taylor-Burton (69.42 carats), the Allnatt (101.29 carats), the De Beers Millennium Star (203.04 carats), the Centenary (273.85 carats), and the Incomparable (407.48 carats).
GIA is the creator of the revolutionary 4Cs of diamond value (carat, color, clarity, and cut). It is also the birthplace of the International Diamond Grading System™. Today, GIA’s D-Z color-grading scale, Flawless–I3 clarity-grading scale and Excellent-to-Poor cut-grading scale are recognized by virtually every professional jeweler and savvy diamond buyer in the world.
Saturday, April 25, 2009
But even a diamond isn’t indestructible. It can be chipped by a sharp blow or become loose in its setting and fall out. A diamond should be worn with care.
Because diamonds tend to pick up grease and oils, they can become dirty with handling and should be occasionally wiped with a lint-free cloth. Other methods for safe cleaning include warm water, mild soap, and a soft toothbrush or a commercial cleaning solution. It is not recommended to use ultrasonic and steam cleaners.
Friday, April 24, 2009
Thursday, April 23, 2009
Of the 4,000+ known minerals, 70 possess qualifications for gemstones, but of these, only approximately 20 are commonly encountered (Hurlbut & Kammerling, 1991, p. 3). These minerals include: diamond, corundum (ruby, sapphire, star ruby and sapphire), beryl (emerald, aquamarine, morganite, goshenite, golden or heliodor), chrysoberyl (cat's eye & alexandrite), spinel, topaz, zircon, tourmaline (indicolite, rubellite, schorl, elbaite), garnet group (almandite/almandine, rhodolite, pyrope, grossular/tsavorite, spessartine, uvarovite), quartz: crystalline (rock crystal, amethyst, citrine, cairngorm or smoky, rose, aventurine, tiger's-eye, rutilated), quartz: cryptocrystalline (chrysoprase, carnelian, sard, bloodstone, agate, onyx, jasper, agatized or petrified wood), olivine peridot (chrysolite), jadeite jade, tremolite-actinolite or nephrite jade, spodumene (kunzite, hiddenite), feldspar group (microcline amazonite, labradorite, orthoclase moonstone, oligoclase sunstone), turquoise, lapis-lazuli, and opal.
Wednesday, April 22, 2009
|Gem||Formula||Color||Origin Of Color|
|Ruby||Al2O3||Red||Cr3+ replacing Al3+ in octahedral sites|
|Emerald||Be3Al2(SiO3)6||Green||Cr3+ replacing Al3+ in octahedral site|
|Alexandrite||Al2BeO4||Red/Green||Cr3+ replacing Al3+ in octahedral site|
|Garnet||Mg3Al2(SiO4)3||Red||Fe2+ replacing Mg2+ in 8-coordinate site|
|Peridot||Mg2SiO4||Yellow-green||Fe2+ replacing Mg2+ in 6-coordinate site|
|Tourmaline||Na3Li3Al6(BO3)3(SiO3)6F4||Pink||Mn2+ replacing Li+ and Al3+ in octahedral site|
|Turquoise||Al6(PO4)4(OH)8A4H2O||Blue-green||Cu2+ coordinated to 4 OHG and 2 H2O|
|Sapphire||Al2O3||Blue||Intervalence transition between Fe2+ and Ti4+ replacing Al3+ in adjacent octahedral sites|
|Aquamarine||Be3Al2(SiO3)6||Blue||Intervalence transition between Fe2+ and Fe3+ replacing Al3+ in adjacent octahedral sites|
|Diamond||C||Colorless pale blue or yellow Color||centers from nitrogen atoms trapped in crystal|
Tuesday, April 21, 2009
Colombia is one of the largest commercial producers of emerald. Fine Colombian emeralds are highly regarded for their excellent color. Zambia is also a commercial source of emeralds with good clarity. Other sources include Afghanistan, Brazil, Pakistan, Russia, and Zimbabwe.
Pearl and Cultured Pearl
Historically, the finest material was mined in Iran and is known as Persian turquoise. This source is no longer commercially important. Today, the United States is the major source of turquoise. Other sources are China, Chile, Australia, and Mexico.
Monday, April 20, 2009
Diamonds occur in two general types of deposits world wide:
- volcanic pipes, also known as kimberlite pipes
- alluvial, or placer, deposits, which were formed by the erosion of diamond pipes over millions of years.
The following is not required information for students of EPS 2
The earliest productive mines were in the Golconda region of India, particularly along the Kristna River. After 1725 this mining district was gradually eclipsed in importance by the diamond deposits of Brazil. Diamonds were first mined there along the Jequitinhonha River, in the Diamantina area of the state of Minas Gerais.
In 1867 a 21-carat stone was discovered on the banks of the Orange River near Hopetown, South Africa. A great diamond rush started, and new deposits were discovered that were more productive than any the world had ever known. Another major diamond resource was developed in the 1950s in the Yakutia region of the Soviet Union. By the 1980s the Yakutia and South African regions and the country of Zaire dominated the world's diamond market. The mineral has also been found in smaller amounts in numerous other places. In the United States the leading producers include Arizona, Nevada, and Montana, although the largest gemstones have been found in an eroded volcanic pipe in Pike County, Ark.
For many years, microscopic diamonds have occasionally been noted in meteorites; they were attributed to high-speed collisions in space or with the Earth. In 1987, however, following the discovery of many more such diamonds, the theory was developed that they are the product of ancient supernova explosions of giant stars.
In recent years, diamonds have been found in unusual metamorphic rocks that were subjected to very high temperatures and pressures.
Sunday, April 19, 2009
Jamaica, N.Y. - On Saturday, Customs and Border Protection officers at JFK International Airport seized almost 1,200 carats in diamonds. The 28 rough diamonds originated from Sierra Leone and were seized because they did not have Kimberley Certificates which are required by the Clean Diamond Trade Act.
The diamonds were destined for Brentwood, N.Y. and had a declared value of more then $800,000.
Two U.S. jewelers, arriving from Sierra Leone via London, declared that they were transporting rough diamonds and 57 pounds of gold dust. The two U.S. citizens, whose names are being withheld for privacy reasons, were referred for a baggage exam to verify proper documentation for entry. Unset stones are generally duty free when imported from most countries; however, a formal entry must be filed on all rough diamonds and all required documents must be available for inspection.
Saturday, April 18, 2009
The Napoléon Diamond Necklace.
Original box of the Napoléon Diamond Necklace, made in Paris.
Details of the Napoléon Diamond Necklace.
Disc-shaped tension halos, probably around sulfide crystals, as inclusions in one of the diamond.
Microscope coupled with an infrared spectrometer used to acquire infrared spectra of diamonds in the Napoleon Necklace.
The Napoléon Diamond Necklace under ultraviolet light. The diamonds are labeled as to their type. Most diamonds exhibit a blue fluorescence with various intensities; several diamonds have a pinkish orange luminescence; the rest are non fluorescent.
Friday, April 17, 2009
Carbonado, commonly known as the 'Black Diamond,' is a natural polycrystalline diamond found in alluvial deposits in the Central African Republic and Brazil. Its natural colour is black or dark grey, and it is more porous than other diamonds.
Recently, scientists studying diamonds have found the ages of thousands of diamonds from Southern Africa, where most diamonds are found. They discovered that there were only three times during Earth’s history when diamonds were made and that Earth no longer makes diamonds like it used to. “Something was different then. Perhaps the planet was hotter on the inside, or the composition of the rocks was subtly different. Whatever it was it has changed now,” stated Steve Shirey, one of the project scientists.
The oldest diamonds were made 3.3 billion years ago when Earth was rather young. The second time diamonds were made was 2.9 billion years ago. The scientists think that these diamonds were probably formed from rocks that lay at the bottom of a shallow sea. The carbon that made these diamonds probably came from ancient sea life. The youngest diamonds on Earth are 1.2 billion years old although a few smaller diamonds are about 100 million years old.
Some people like diamonds because they are pretty, rare, or expensive but Dr. Steve Shirey has a different view. “I think of diamonds,” he said, “as being tiny time capsules that encase a little piece of rock protecting it for billions of years and providing us with a unique window on ancient times.”
Thursday, April 16, 2009
- The diamond is the official gem of the Northwest Territories.
- The discovery of diamonds in 1991, at Lac De Gras resulted in the largest staking rush in Canadian history.
- BHP’s Ekati mine in the NWT was Canada’s first diamond mine. Construction began in 1997 and it opened officially on October 14, 1998.
- Since 1998, about 78,947,507 carats worth of gem quality diamonds have been mined in the NWT – with an estimated value of $11.368 billion/CAD.
- De Beers’ Snap Lake Mine is Canada’s first fully underground diamond operation – and the first mine ever built by the world’s diamond giant outside of Africa.
- The collective operations of the Ekati, Diavik and Snap Lake diamond mines are producing 15% of the world’s rough diamonds. Diamond production for 2007 reached 16.6 million carats worth $1.4 billion.
- Canada is the third largest diamond producer by value in the world after Botswana and Russia.
- Since 1996, the NWT’s diamond mines have provided over 16,000 person years of employment – over 4,400 to Aboriginal residents and have surpassed $5 billion in investment with northern and Aboriginal businesses.