Jewelry: Diamonds

Terms Carat Weight Clarity Color Cut

Diamond is one of the two best known forms (or allotropes) of carbon, whose hardness and high dispersion of light makes it useful for industrial applications and jewelry. The other equally well known allotrope is graphite; but diamonds are specifically renowned as a mineral with superlative physical qualities. They make excellent abrasives because they can only be scratched by other diamonds, which also means they hold a polish extremely well and retain luster. About 130 million carats (26,000 kg) are mined annually, with a total value of nearly 9 billion US$. The name "diamond" derives from the ancient Greek adamas (αδάμας; "impossible to tame"). They have been treasured as gems since their use as religious icons in India at least 2,500 years ago—and usage in drill bits and engraving tools also dates to early human history. Popularity of diamonds has risen since the 19th century because of improved cutting and polishing techniques, and they are commonly judged by the "four Cs": carat, clarity, color, and cut. Nearly four times the mass of natural diamonds are produced as synthetic diamond each year, though these are typically classified with poor-quality specimens that are suitable only for industrial-grade use. Most natural diamonds originate from central and southern Africa, although significant sources of the mineral have been discovered in Canada, Russia, Brazil, and Australia. They are generally mined from volcanic pipes, which are deep in the Earth where the high pressure and temperature enables the formation of the crystals. The mining and distribution of natural diamonds are subjects of frequent controversy—such as with concerns over the sale of conflict diamonds by African paramilitary groups. There are also allegations that the De Beers Group misuses its dominance in the industry to control supply and manipulate price via monopolistic practices. Crystal structure Diamonds typically crystallize in the cubic crystal system and consist of tetrahedrally bonded carbon atoms. Lonsdaleite is a polymorph of diamond (and a distinct mineral species) that crystallizes with hexagonal symmetry; it is rarely found in nature, but is characteristic of synthetic diamonds. A cryptocrystalline variety of diamond is called carbonado. A colorless, grey or black diamond with a tiny radial structure is a spherulite. The tetrahedral arrangement of atoms in a diamond crystal is the source of many of diamond's properties; graphite, another allotrope of carbon, has a rhombohedral crystal structure and as a result shows dramatically different physical characteristics—contrary to diamond, graphite is a very soft, dark grey, opaque mineral. Hardness Diamond is the hardest known naturally occurring material, scoring 10 on the relative Mohs scale of mineral hardness and having an absolute hardness value of between 167 and 231 gigapascals in various tests. Diamond's hardness has been known since antiquity, and is the source of its name. However, aggregated diamond nanorods, an allotrope of carbon first synthesized in 2005, are now believed to be even harder than diamond. Industrial use of diamonds has historically been associated with their hardness; this property makes diamond the ideal material for cutting and grinding tools. It is one of the most known and most useful of more than 3,000 known minerals. As the hardest known naturally occurring material, diamond can be used to polish, cut, or wear away any material, including other diamonds. Common industrial adaptations of this ability include diamond-tipped drill bits and saws, or use of diamond powder as an abrasive. Other specialized applications also exist or are being developed, including use as semiconductors: some blue diamonds are natural semiconductors, in contrast to most other diamonds, which are excellent electrical insulators. Industrial-grade diamonds are either unsuitable for use as gems or synthetically produced, which lowers their price and makes their use economically feasible. Industrial applications, especially as drill bits and engraving tools, also date to ancient times. The hardness of diamonds also contributes to its suitability as a gemstone. Because it can only be scratched by other diamonds, it maintains its polish extremely well, keeping its luster over long periods of time. Unlike many other gems, it is well-suited to daily wear because of its resistance to scratching—perhaps contributing to its popularity as the preferred gem in an engagement ring or wedding ring, which are often worn everyday. Toughness Unlike hardness, which only denotes resistance to scratching, diamond's toughness is only fair to good. Toughness relates to a material's ability to resist breakage from forceful impact. As with any material, the macroscopic geometry of a diamond contributes to its resistance to breakage. Diamonds cut into certain particular shapes are therefore more prone to breakage than others. Color Diamonds occur in a variety of transparent hues — colorless, white, steel, blue, yellow, orange, red, green, pink, brown—or colored black. Diamonds with a detectable hue to them are known as colored diamonds. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless. Most diamond impurities replace a carbon atom in the crystal lattice. The most common impurity, nitrogen, causes a yellowish or brownish tinge. Thermodynamic stability At surface air pressure (one atmosphere), diamonds are not as stable as graphite, and so the decay of diamond is thermodynamically favorable (ΔG = −2.99 kJ / mol). Diamonds will burn at approximately 800 degrees Celsius, providing that enough oxygen is available. This was shown in the late 18th century, and previously described during Roman times. So, despite the popular advertising slogan, diamonds are not forever. However, owing to a very large kinetic energy barrier, diamonds are metastable; under normal conditions, it would take an extremely long time (possibly more than the age of the Universe) for diamond to decay into graphite. Electromagnetic properties Optical properties Diamonds exhibit a high dispersion of visible light. This strong ability to split white light into its component colors is an important aspect of diamond's attraction as a gemstone, giving it impressive prismatic action that results in so-called fire in a well-cut stone. The luster of a diamond, a characterization of how light interacts with the surface of a crystal, is brilliant and is described as adamantine, which simply means diamond-like. This is owed to their high refractive index of 2.417 (at 589.3 nm), which causes total internal reflection to occur. Some diamonds exhibit fluorescence of various colors under long wave ultraviolet light, but generally show bluish-white, yellowish or greenish fluorescence under X-rays. Some diamonds show no fluorescence. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Diamonds.

Jewelry: Diamonds

As a gemstone, Diamond's single flaw (perfect cleavage) is far outdistanced by the sum of its positive qualities. It has a broad color range, high refraction, high dispersion or fire, very low reactivity to chemicals, rarity, and of course, extreme hardness and durability. Diamond is the April Birthstone.

In terms of it's physical properties, diamond is the ultimate mineral in several ways:

• Hardness: Diamond is a perfect "10", defining the top of the hardness scale.
• Clarity: Diamond is transparent over a larger range of wavelengths (from the ultraviolet into the far infrared) than is any other solid or liquid substance - nothing else even comes close.
• Thermal Conductivity: Diamond conducts heat better than anything - five times better than the second best element, Silver!
• Melting Point: Diamond has the highest melting point (3820 degrees Kelvin)!
• Lattice Density: The atoms of Diamond are packed closer together than are the atoms of any other substance!

Israel Diamonds Exports Grow By 6%

Ramat Gan ----July 5..... Israel net polished diamonds export industry rose 6% from January to June 2005, according to statistics reported by the Israel Ministry of Industry, Trade and Labor's Diamond Controller, Shmuel Mordechai.

Why Buy Diamonds from Israel?

Israel is one of the world’s leading diamond manufacturing and trading centers, selling to numerous markets over the world. Israel sold over $6.3 billion worth of polished diamonds in 2004 for the following main reasons: half of all gem quality diamonds sold around the world are coming from Israel.

Israel is the largest consumer of rough diamonds in the world. Israel produces high quality diamonds, based on expert craftsmanship combined with innovative technology. From lasers to robotics, Israel is at the forefront of technological advances in diamond manufacture.

The Israel Diamond Exchange is the largest in the world, offering the greatest selection of diamonds under one roof. Buying in Israel is safe and convenient – the Diamond Exchange complex is a virtual citadel, where diamonds are traded in complete security. Israeli diamantaires are reliable, flexible and gear themselves to clients’ needs. Israel leads the world diamond industry in innovating new cuts.

Diamond Fats

Diamond Facts

• The largest Diamond ever found:
  Cullinan at 3,106 carats.
• What is the hardest natural substance on Earth?
  The Diamond.
• 80% of the world's diamonds are not suitable for Jewelry.
• Is a Diamond Indestructible?
  No. The fact that Diamonds are a hard substance refers to their ability to withstand scratching. But that is different than toughness, which refers to the ability to withstand breaking or cleavage.
• How old are most diamonds which are found in nature?
  1 billion to 3 billion years, by most accounts.
• How do diamonds reach us?
  They are formed deep within the Earth's crust, and come to the surface via Volcanoes. Most diamonds are found in Kimberlite, which is volcanic rock.

Diamonds

Diamond is the hardest known natural material (third-hardest known material after aggregated diamond nanorods and ultra hard fullerite), whose hardness and high dispersion of light make it useful for industrial applications and jewelry.

Diamonds are specifically renowned as a material with superlative physical qualities — they make excellent abrasives because they can be scratched only by other diamonds, Borazon, ultra hard fullerite, or aggregated diamond nanorods, which also means they hold a polish extremely well and retain their luster. About 130 million carats (26,000 kg) are mined annually, with a total value of nearly USD $9 billion. About 100,000 kg are synthesized annually.

The name “diamond” derives from the ancient Greek adamas (αδάμας; “invincible”). They have been treasured as gemstones since their use as religious icons in India at least 2,500 years ago— and usage in drill bits and engraving tools also dates to early human history. Popularity of diamonds has risen since the 19th century because of increased supply, improved cutting and polishing techniques, growth in the world economy, and innovative and successful advertising campaigns. They are commonly judged by the “four Cs”: carat, clarity, color, and cut.

Roughly 49% of diamonds originate from central and southern Africa, although significant sources of the mineral have been discovered in Canada, India, Russia, Brazil, and Australia. They are mined from kimberlite and lamproite volcanic pipes, which brought to the surface the diamond crystals from deep in the Earth where the high pressure and temperature enables the formation of the crystals. The mining and distribution of natural diamonds are subjects of frequent controversy such as with concerns over the sale of conflict diamonds by African paramilitary groups. There are also allegations that the De Beers Group misuses its dominance in the industry to control supply and manipulate price via monopolistic practices, although in recent years the company's market share has dropped to below 50%.

Material properties

A diamond is a transparent crystal of tetrahedrally bonded carbon atoms. Diamonds have been adapted for many uses because of the material's exceptional physical characteristics. Most notable are its extreme hardness, its high dispersion index, and high thermal conductivity.

Hardness

Diamond is the hardest natural material known, its hardness set to 10, i.e. hardest, on Mohs scale of mineral hardness and having an absolute hardness value of between 90, 167, and 231 gigapascals in various tests. Diamond's hardness has been known since antiquity, and is the source of its name. However, aggregated diamond nanorods, an allotrope of carbon first synthesized in 2005, are now believed to be even harder than diamond.

The hardest diamonds in the world are from the New England area in New South Wales, Australia. These diamonds are generally small, perfect to semiperfect octahedra, and are used to polish other diamonds. Their hardness is considered to be a product of the crystal growth form, which is single stage growth crystal. Most other diamonds show more evidence of multiple growth stages, which produce inclusions, flaws, and defect planes in the crystal lattice all of which affect their hardness.

The hardness of diamonds contributes to its suitability as a gemstone. Because it can only be scratched by other diamonds, it maintains its polish extremely well, keeping its luster over long periods of time. Unlike many other gems, it is well-suited to daily wear because of its resistance to scratching—perhaps contributing to its popularity as the preferred gem in an engagement ring or wedding ring, which are often worn every day.

Industrial use of diamonds has historically been associated with their hardness; this property makes diamond the ideal material for cutting and grinding tools. As the hardest known naturally occurring material, diamond can be used to polish, cut, or wear away any material, including other diamonds. Common industrial adaptations of this ability include diamond-tipped drill bits and saws, or use of diamond powder as an abrasive. Industrial-grade diamonds are either unsuitable for use as gems or synthetically produced, which lowers their value and makes their use economically feasible. Industrial applications, especially as drill bits and engraving tools, also date to ancient times.

Electrical conductivity

Other specialized applications also exist or are being developed, including use as semiconductors: some blue diamonds are natural semiconductors, in contrast to most other diamonds, which are excellent electrical insulators.

Toughness

Toughness relates to a material's ability to resist breakage from forceful impact. The toughness of natural diamond has been measured as 3.4 MPa\sqrt{m} , which is good compared to other gemstones, but poor compared to most engineering materials. As with any material, the macroscopic geometry of a diamond contributes to its resistance to breakage. Diamond is therefore more fragile in some orientations than others.

Color

Diamonds can occur in nearly any color, though yellow and brown are by far the most common. "Black" diamonds are not truly black, but rather contain numerous dark inclusions that give the gems their dark appearance. When the color is saturated enough in yellow or brown diamonds, a stone may be referred to as a fancy colored diamond by the gem trade, otherwise they are graded for color in the normal color range of white diamonds. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless. Most diamond impurities replace a carbon atom in the crystal lattice, known as a carbon flaw. The most common impurity, nitrogen, causes a slight to intense yellow coloration depending upon the type and concentration of nitrogen present. The Gemological Institute of America (GIA) classifies low saturation yellow and brown diamonds as diamonds in the normal color range, and applies a grading scale from 'D' (colorless) to 'Z' (light yellow). The GIA labels diamonds that have more color than a 'Z' diamond fancy, along with those that are any color other than yellow or brown.

Natural history

Formation

Diamonds are formed in numerous different ways. One way they are formed is by prolonged exposure of carbon-bearing materials to high pressure at comparatively low temperature. On Earth, the formation of diamonds is possible because there are regions deep within the Earth that are at a high enough pressure and low enough temperature that the formation of diamonds is thermodynamically favorable. Beneath thick continental crust ( in the lithospheric mantle of cratons), diamonds form starting at depths of about 150 kilometers (90 miles), where pressure is roughly 5 gigapascals and the temperature is around 1200 degrees Celsius (2200 degrees Fahrenheit). Diamonds rise to the Earth surfaces carried by the molten rock of kimberlite or lamproite diatremes. Diamonds cannot form beneath oceanic crust because the oceanic mantle is too hot at the appropriate depth. Thick continental lithosphere is cooler than asthenosphere at the same depth, reaching the required pressure at a low enough temperature for diamond stability. Long residence in the cratonic lithosphere allows diamond crystals to grow larger.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Diamonds.

Diamond -- History

Diamonds are thought to have been first recognized and mined in India, where significant alluvial deposits of the stone could then be found. The earliest written reference can be found in the Buddhist text, the Anguttara Nikaya another sanskrit text, the Arthashastra, which was completed around 296 BCE and describes diamond's hardness, luster, and dispersion. Diamonds quickly became associated with divinity, being used to decorate religious icons, and were believed to bring good fortune to those who carried them. Ownership was restricted among various castes by color, with only kings being allowed to own all colors of diamond.

In February 2005, a joint Chinese-U.S. team of archaeologists reported the discovery of four corundum-rich stone ceremonial burial axes originating from China's Liangzhu and Sanxingcun cultures (4000 BCE–2500 BCE) which, because of the axes' specular surfaces, the scientists believe were polished using diamond powder [2] [3]. Although there are diamond deposits now known to exist close to the burial sites, no direct evidence of coeval diamond mining has been found: the researchers came to this conclusion by polishing corundum using various lapidary abrasives and modern techniques then comparing the results using an atomic force microscope. At that scale, the surface of the modern diamond-polished corundum closely resembled that of the axes; however, the polishes of the latter were superior.

Diamonds were traded to both the east and west of India and were recognized by various cultures for their gemological or industrial uses. In his work Naturalis Historia, the Roman writer Pliny the Elder noted diamond's ornamental uses, as well as its usefulness to engravers because of its hardness. In China, diamonds seem to have been used primarily as diamond tools for engraving jade and drilling holes in beads. Archaeological evidence from Yemen suggests that diamonds were used as drill tips as early as the 4th century BCE. In Europe, however, diamonds disappeared for almost 1,000 years following the rise of Christianity because of two effects: early Christians rejected diamonds because of their earlier use in amulets, and Arabic traders restricted the flow of trade between Europe and India.


Until the late Middle Ages, diamonds were most prized in their natural octahedral state, perhaps with the crystal surfaces polished to increase luster and remove foreign material. Around 1300, the flow of diamonds into Europe increased via Venice's trade network, with most flowing through the low country ports of Bruges, Antwerp, and Amsterdam. During this time, the taboo against cutting diamonds into gem shapes, which was established over 1,000 years earlier in the traditions of India, ended allowing the development of diamond cutting technology to begin in earnest. By 1375, a guild of diamond polishers had been established at Nuremberg. Over the following centuries, various diamond cuts were introduced which increasingly demonstrated the fire and brilliance that makes diamonds treasured today: the table cut, the briolette (around 1476), the rose cut (mid-16th century), and by the mid-17th century, the Mazarin, the first brilliant cut diamond design. In 1919, Marcel Tolkowsky developed an ideal round brilliant cut design that has set the standard for comparison of modern gems; however, diamond cuts have continued to be refined.

The rise in popularity of diamonds as gems seems to have paralleled increasing availability through European history. In the 13th century, King Louis IX of France established a law that only the king could own diamonds. However, within a century diamonds were popular gems among the moneyed aristocratic and merchant classes, and by 1477 had begun to be used in wedding rings. Popularity continued to rise as new cuts were developed that enhanced the diamond's aesthetic appeal, and has largely continued unabated to this day; diamonds have proven popular with all classes in society as their cost has become within reach. A number of large diamonds have become historically significant objects, as their inclusion in various sets of crown jewels and the purchase, sale, and sometimes theft of notable diamonds, have sometimes become politicized.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Diamonds.