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Thursday, June 18, 2009

Certificated Diamonds

Most diamonds are graded by the retailer from experience and via merchant agreements. We insist that our merchants supply at least the minimum standard that we state and then we check every stone ourselves. We warrant the grading in writing on our valuations, each of which is personally signed by a director of this company. We also offer this collection of 232 pieces set with independently certificated stones. Each is supplied with its own unique certifiicate specifying its quality. You can read more about diamonds here.


Here we offer a collection of 244 quality gold and platinum jewelled earrings for pierced ears. Every pair of earrings that we sell is hand finished and inspected in our own workshops. This takes a little time but we believe it's essential to ensure the perfect quality of your earrings. We offer many gemstones including diamonds, tanzanite's, sapphire, amethysts and many more. You can read more about gemstones here.

Wedding Rings

Your wedding ring represents continuity and commitment in the form of a constant and unbroken band. Here we offer a collection of 84 Ampalian wedding rings made with care to be presented as a symbol of love to last a lifetime. Every wedding ring that we sell is hand finished and inspected in our own workshops. This takes a little time but we believe it's essential to ensure the perfect quality of your wedding ring. You can read more about wedding rings here.

Wednesday, June 17, 2009

Eternity Rings

Your eternity ring represents ongoing love and commitment deep into your relationship. Here we offer a collection of 663 quality gold and platinum eternity rings. Every eternity ring that we sell is hand finished and inspected in our own workshops. This takes a little time but we believe it's essential to ensure the perfect quality of your ring to be treasured for a lifetime and beyond. You can read more about eternity rings here.

Thermal properties

Thermal properties

One of many remarkable properties of diamond is its unsurpassed thermal conductivity. With a value of 2000 W/mK it exceeds that of copper by a factor of five. In contrast to metals, where heat is conducted by electrons, lattice vibrations are responsible for diamond's high thermal conductivity.

For thermal management applications, the outstanding thermal conductivity and diffusivity of diamond is an essential. Nowadays CVD diamond is used as submounts for high-power integrated circuits and laser diodes.

Thermal conductivity @300K > 1800 W/mK
Thermal Expansion Coefficient
@300K 1.0×10-6 K-1
Spectral Specific Heat 5.02 J/kgK

Necklaces & Pendants

A necklace is an article of clothing or jewelry; which is worn around the neck. Necklaces are frequently formed from a metal chain; often attached to a locket or pendant. Necklaces can also be manufactured with cloth, and they sometimes contain rocks (particularly gems), wood, and/or shells. When worn high on the neck it is referred to as a choker. Many Christians wear a cross or crucifix which differs in shape, size, material and color. Others wear the cross merely out of decoration and may not be Christian. Historically women initially wore necklaces to draw attention to the cleavage region.


A diamond simulant is defined as a non-diamond material that is used to simulate the appearance of a diamond. Diamond-simulant gems are often referred to as diamante. The most familiar diamond simulant to most consumers is cubic zirconia. The popular gemstone moissanite (silicon carbide) is often treated as a diamond simulant, although it is a gemstone in its own right. While moissanite does look similar to diamond, its main disadvantage as a diamond simulant is that cubic zirconia is far cheaper and arguably equally convincing. Both cubic zirconia and moissanite are produced synthetically.[74]


popular method of growing synthetic diamond is chemical vapor deposition (CVD). The growth occurs under low pressure (below atmospheric pressure). It involves feeding a mixture of gases (typically 1 to 99 methane to hydrogen) into a chamber and splitting them to chemically active radicals in a plasma ignited by microwaves, hot filament, arc discharge, welding torch or laser.[73] This method is mostly used for coatings, but can also produce single crystals several millimeters in size (see picture).[51]

At present, the annual production of gem quality synthetic diamonds is only a few thousand carats, whereas the total production of natural diamonds is around 120 million carats. Despite this fact, a purchaser is more likely to encounter a synthetic when looking for a fancy-colored diamond because nearly all synthetic diamonds are fancy-colored, while only 0.01% of natural diamonds are fancy-colored.[11] Producing large synthetic diamonds threatens the business model of the diamond industry. The ultimate effect of the ready availability of gem-quality diamonds at low cost in the future is hard to predict.


A large trade in gem-grade diamonds exists. Unlike precious metals such as gold or platinum, gem diamonds do not trade as a commodity: there is a substantial mark-up in the retail sale of diamonds. Contrary to popular belief, there is a well-established market for resale of polished diamonds (e.g. pawnbroking, auctions, second-hand jewelry stores, diamantaires, bourses, etc.). One hallmark of the trade in gem-quality diamonds is its remarkable concentration: wholesale trade and diamond cutting is limited to just a few locations. 92% of diamond pieces cut in 2003 were in Surat, Gujarat, India.[40] Other important centers of diamond cutting and trading are Antwerp, where the International Gemological Institute is based, London, New York, Tel Aviv, and Amsterdam. A single company—De Beers—controls a significant proportion of the trade in diamonds. They are based in Johannesburg, South Africa and London, England. One contributory factor is the geological nature of diamond deposits: several large primary kimberlite-pipe mines each account for significant portions of market share (such as the Jwaneng mine in Botswana, which is a single large pit operated by De Beers that can produce between 12.5 to 15 million carats of diamonds per year[41]), whereas secondary alluvial diamond deposits tend to be fragmented amongst many different operators because they can be dispersed over many hundreds of square kilometers (e.g., alluvial deposits in Brazil).

The production and distribution of diamonds is largely consolidated in the hands of a few key players, and concentrated in traditional diamond trading centers. The most important being Antwerp, where 80% of all rough diamonds, 50% of all cut diamonds and more than 50% of all rough, cut and industrial diamonds combined are handled.[42] This makes Antwerp the de facto 'world diamond capital'. New York, however, along with the rest of the United States, is where almost 80% of the world's diamonds are sold, including auction sales. Also, the largest and most unusually shaped rough diamonds end up in New York.[42] The De Beers company, as the world's largest diamond miner holds a clearly dominant position in the industry, and has done so since soon after its founding in 1888 by the British imperialist Cecil Rhodes. De Beers owns or controls a significant portion of the world's rough diamond production facilities (mines) and distribution channels for gem-quality diamonds. The company and its subsidiaries own mines that produce some 40 percent of annual world diamond production. At one time it was thought over 80 percent of the world's rough diamonds passed through the Diamond Trading Company (DTC, a subsidiary of De Beers) in London,[43] but presently the figure is estimated at around 40 percent.[44] De Beers sold off the vast majority its diamond stockpile in the late 1990s - early 2000s[45] and the remainder largely represents working stock (diamonds that are being sorted before sale).[46] This was well documented in the press[47] but remains little known to the general public.

Material properties of diamond

Diamond is the allotrope of carbon where the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. Diamond is an optically isotropic crystal that is transparent to opaque. It is the hardest naturally occurring material known, due to its strong covalent bonding, yet its toughness is only fair to good due to important structural weaknesses. The precise tensile strength of diamond is unknown, however strength up to 60 GPa has been observed, and it could be as high as 90-225 GPa depending on crystal direction.[1] The anisotropy of diamond hardness is carefully considered during diamond cutting. Diamond has a high refractive index (2.417) and moderate dispersion (0.044) properties which give cut diamonds their brilliance. Scientists classify diamonds into two main types, I and II, and four subtypes (Ia, Ib, IIa and IIb), depending on the nature of crystallographic defects present. Trace impurities substitutionally replacing carbon atoms in a diamond's crystal lattice, and in some cases structural defects, are responsible for the wide range of colors seen in diamond. Most diamonds are electrical insulators but extremely efficient thermal conductors. The specific gravity of single-crystal diamond (3.52) is fairly constant. Contrary to a common misconception,[by whom?] diamond is not the most stable form of solid carbon; graphite has that distinction.


The luster of a diamond is described as 'adamantine', which simply means diamond-like. Reflections on a properly cut diamond's facets are undistorted, due to their flatness. The refractive index of diamond (as measured via sodium light, 589.3 nm) is 2.417. Because it is cubic in structure, diamond is also isotropic. Its high dispersion of 0.044 (variation of refractive index across the visible spectrum) manifests in the perceptible fire of cut diamonds. This fire—flashes of prismatic colors seen in transparent stones—is perhaps diamond's most important optical property from a jewelry perspective. The prominence or amount of fire seen in a stone is heavily influenced by the choice of diamond cut and its associated proportions (particularly crown height), although the body color of fancy diamonds may hide their fire to some degree.[15]

Many other minerals have higher dispersion than diamond: sphene 0.051, andradite 0.057, cassiterite 0.071, SrTiO3 0.109, sphalerite 0.156, synthetic rutile 0.330 ![18] However, the combination of dispersion with extreme hardness, wear and chemical resistivity, as well as clever marketing, determines the exceptional value of diamond as a gemstone.

Color and its causes

Diamonds occur in a restricted variety of colors — black, brown, yellow, gray, white, blue, orange, purple to pink and red. Colored diamonds contain crystallographic defects, including substitutional impurities and structural defects, that cause the coloration. Theoretically, pure diamonds would be transparent and colorless. Diamonds are scientifically classed into two main types and several subtypes, according to the nature of defects present and how they affect light absorption:[4]

Type I diamond has nitrogen (N) atoms as the main impurity, at a concentration of up to 1%. If the N atoms are in pairs or larger aggregates, they do not affect the diamond's color; these are Type Ia. About 98% of gem diamonds are type Ia: these diamonds belong to the Cape series, named after the diamond-rich region formerly known as Cape Province in South Africa, whose deposits are largely Type Ia. If the nitrogen atoms are dispersed throughout the crystal in isolated sites (not paired or grouped), they give the stone an intense yellow or occasionally brown tint (type Ib); the rare canary diamonds belong to this type, which represents only ~0.1% of known natural diamonds. Synthetic diamond containing nitrogen is usually of type Ib. Type Ia and Ib diamonds absorb in both the infrared and ultraviolet region, from 320 nm. They also have a characteristic fluorescence and visible absorption spectrum (see Optical properties).[12]

Type II diamonds have very few if any nitrogen impurities. Pure (type IIa) diamond can be colored pink, red, or brown due to structural anomalies arising through plastic deformation during crystal growth[13] — these diamonds are rare (1.8 percent of gem diamonds), but constitute a large percentage of Australian diamonds. Type IIb diamonds, which account for ~0.1% of gem diamonds, are usually a steely blue or gray due to boron atoms scattered within the crystal matrix. These diamonds are also semiconductors, unlike other diamond types (see Electrical properties). Most blue-gray diamonds coming from the Argyle mine of Australia are not of type IIb, but of Ia type. Those diamonds contain large concentrations of defects and impurities (especially hydrogen and nitrogen) and the origin of their color is yet uncertain.[14] Type II diamonds weakly absorb in a different region of the infrared (which absorption is due to the diamond lattice rather than impurities), and transmit in the ultraviolet below 225 nm, unlike type I diamonds. They also have differing fluorescence characteristics, but no discernible visible absorption spectrum.[12]
Color in irradiated diamonds, with (two left stones) and without annealing (right)

Certain diamond enhancement techniques are commonly used to artificially produce an array of colors, including blue, green, yellow, red, and black. Color enhancement techniques usually involve irradiation, including proton bombardment via cyclotrons; neutron bombardment in the piles of nuclear reactors; and electron bombardment by Van de Graaff generators. These high-energy particles physically alter the diamond's crystal lattice, knocking carbon atoms out of place and producing color centers. The depth of color penetration depends on the technique and its duration, and in some cases the diamond may be left radioactive to some degree.[4][15]

It should be noted that some irradiated diamonds are completely natural — one famous example is the Dresden Green Diamond.[16] In these natural stones the color is imparted by "radiation burns" (natural irradiation by alpha particles originating from uranium ore) in the form of small patches, usually only microns deep. Additionally, Type IIa diamonds can have their structural deformations "repaired" via a high-pressure high-temperature (HPHT) process, removing much or all of the diamond's color.

Tuesday, June 16, 2009

Substantial conductivity

Substantial conductivity is commonly observed in nominally undoped diamond grown by chemical vapor deposition. This conductivity is associated with hydrogen-related species adsorbed at the surface, and it can be removed by annealing or other surface treatments.[

Harmful substances for Diamond

These substances can scratch diamond:

  • Some diamonds are harder than others.
  • Nanocrystalline diamond aggregates produced by high-pressure high-temperature treatment of graphite or fullerite (C60).[19]
  • Cubic Boron nitride (Borazon)
  • A hexagonal form of diamond called lonsdaleite, which is theoretically predicted to be 58% stronger than diamond.[20]

Industrial use of diamonds

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, and the use of diamond powder as an abrasive. Less expensive industrial-grade diamonds, known as bort, with more flaws and poorer color than gems, are used for such purposes.[17]

Diamond suitability

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. 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 engagement or wedding rings, which are often worn every day.

Diamond hardness associated wirh

Their hardness is associated with the crystal growth form, which is single-stage crystal growth. 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.[15] It is possible to treat regular diamonds under a combination of high pressure and high temperature to produce diamonds that are harder than the diamonds used in hardness gauges.[16]

diamond's natural hardness

The hardest natural diamonds in the world are from the Copeton and Bingara fields located in the New England area in New South Wales, Australia. They were called can-ni-faire ("cannot be processed"—a combination of English "can", Italian "ni" = not and French "faire" = do[14]) by the cutters in Antwerp when they started to arrive in quantity from Australia in the 1870s. These diamonds are generally small, perfect to semiperfect octahedra, and are used to polish other diamonds.

Diamond hardness

Diamond is the hardest natural material known, where hardness is defined as resistance to scratching.[12] Diamond has a hardness of 10 (hardest) on Mohs scale of mineral hardness.[13] Diamond's hardness has been known since antiquity, and is the source of its name.

Diamond properties

A diamond is a transparent crystal of tetrahedrally bonded carbon atoms (sp3) that crystallizes into the diamond lattice which is a variation of the face centered cubic structure. Diamonds have been adapted for many uses because of the material's exceptional physical characteristics. Most notable are its extreme hardness and thermal conductivity (900–2,320 W/(m·K))[8], as well as wide bandgap and high optical dispersion.[9] Above 1,700 °C (1,973 K / 3,583 °F) in vacuum or oxygen-free atmosphere, diamond converts to graphite; in air, transformation starts at ~800 °C.[10] Naturally occurring diamonds have a density ranging from 3.15–3.53 g/cm3, with very pure diamond typically extremely close to 3.52 g/cm3.[11]

The most familiar usage of diamonds

The most familiar usage of diamonds today is as gemstones used for adornment, a usage which dates back into antiquity. The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds. In the twentieth century, experts in the field of gemology have developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem. Four characteristics, known informally as the four Cs, are now commonly used as the basic descriptors of diamonds: these are carat, cut, color, and clarity.

Diamonds as gemstones

Diamonds have been treasured as gemstones since their use as religious icons in ancient India. Their usage in engraving tools also dates to early human history.[4][5] 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.[6]

Diamond is History

The name diamond is derived from the ancient Greek ἀδάμας (adámas), "proper", "unalterable", "unbreakable, untamed", from ἀ- (a-), "un-" + δαμάω (damáō), "I overpower, I tame".[2] However, diamonds are thought to have been first recognized and mined in India, where significant alluvial deposits of the stone could then be found many centuries ago along the rivers Penner, Krishna and Godavari. Diamonds have been known in India for at least 3,000 years but most likely 6,000 years.[3]

Most natural diamonds

Most natural diamonds are formed at high-pressure high-temperature conditions existing at depths of 140 km to 190 km in the Earth mantle. Carbon-containing minerals provide the carbon source, and the growth occurs over periods from 1 billion to 3.3 billion years, which respectively corresponds to roughly 25% and 75% of the age of the Earth. Diamonds are brought close to the Earth surface through deep volcanic eruptions by a magma, which cools into igneous rocks known as kimberlites and lamproites. Diamonds can also be produced synthetically in a high-pressure high-temperature process which approximately simulates the conditions in the Earth mantle. An alternative, and completely different growth technique is chemical vapor deposition. Several non-diamond materials, which include cubic zirconia and silicon carbide and are often called diamond simulants, resemble diamond in appearance and many properties. Special gemological techniques have been specially developed to distinguish natural and synthetic diamonds and diamond simulants

Diamond remarkable characteristics

Diamond has remarkable optical characteristics. Because of its extremely rigid lattice, it can be contaminated by only few types of impurities, such as boron and nitrogen. Combined with the wide transparency (corresponding to the wide band gap of 5.5 eV), this results in clear, colorless appearance of most natural diamonds. Small amounts of defects or impurities (about one part per million) color diamond blue (boron), yellow (nitrogen), brown (lattice defects), green, purple, pink, orange or red. Diamond also has relatively high optical dispersion, that is ability to disperse light of different colors, which results in its characteristic luster. Excellent optical and mechanical properties, combined with efficient marketing, make diamond the most popular gemstone.

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