Diamond as a Gift
Are you thinkig a Christmas Gift for you special someone. You can consider to gift of a lifetime as a symbol of your unconditional love. You can give a precious Diamond.
A scattering of round-brilliant cut diamonds shows off the many reflecting facets.
General
In mineralogy, diamond (from the ancient Greek ἀδάμας - adámas "unbreakable") is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions. Diamond is renowned as a material with superlative physical qualities, most of which originate from the strong covalent bonding between its atoms. In particular, diamond has the highest hardness and thermal conductivity of any bulk material. Those properties determine the major industrial application of diamond in cutting and polishing tools.
Diamond has remarkable optical characteristics. Because of its extremely rigid lattice, it can be contaminated by very few types of impurities, such as boron and nitrogen. Combined with the wide transparency, this results in the clear, colorless appearance of most natural diamonds. Small amounts of defects or impurities (about one per million of lattice atoms) 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.
Most natural diamonds are formed at high-pressure high-temperature conditions existing at depths of 140 to 190 kilometers (87 to 120 mi) 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 (25% to 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.
Contents
1 History
2 Material properties
2.1 Hardness
2.2 Electrical conductivity
2.3 Color
2.4 Identification
3 Natural history
3.1 Formation in cratons
3.2 Formation in meteorite impact craters
3.3 Extraterrestrial formation
3.4 Surfacing
4 Production
4.1 Controversial sources
5 Commercial markets
5.1 Gemstones and their distribution
5.1.1 Marketing
5.1.2 Cutting
5.2 Industrial uses
6 Synthetics, simulants, and enhancements
6.1 Synthetics
6.2 Simulants
6.3 Enhancements
6.4 Identification
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".[3] Diamonds are thought to have been first recognized and mined in India, where significant alluvial deposits of the stone could 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.
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. The 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.
In 1813, Humphry Davy used a lens to concentrate the rays of the sun on a diamond in an atmosphere of oxygen, and showed that the only product of the combustion was carbon dioxide, proving that diamond is composed of carbon. Later, he showed that in an atmosphere devoid of oxygen, diamond is converted to graphite.
The most familiar use of diamonds today is as gemstones used for adornment, a use 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 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.[9] A large, flawless diamond is known as a paragon.
Material properties
Main articles: Material properties of diamond and Crystallographic defects in diamond
Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in structure.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−1•K−1),[10] as well as wide bandgap and high optical dispersion.[11] 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 ~700 °C.[12] Naturally occurring diamonds have a density ranging from 3.15–3.53 g/cm3, with pure diamond close to 3.52 g/cm3.[1] Despite the hardness of diamonds, the chemical bonds that hold the carbon atoms in diamonds together are weaker than those that hold together the other form of pure carbon, graphite. The difference is that in diamonds, the bonds form an inflexible three-dimensional lattice. In graphite, the atoms are tightly bonded into sheets, which can slide easily over one another.
Hardness
Diamond is the hardest natural material known, where hardness is defined as resistance to scratching and is graded between 1 (softest) and 10 (hardest) using the Mohs scale of mineral hardness. Diamond has a hardness of 10 (hardest) on this scale.[14] Diamond's hardness has been known since antiquity, and is the source of its name.
The diamond hardness depends on its purity, crystalline perfection and orientation: hardness is higher for flawless, pure crystals oriented to the <111> direction (along the longest diagonal of the cubic diamond lattice).[15] Therefore, whereas it might be possible to scratch some diamonds with other materials, such as boron nitride, the hardest diamonds can only be scratched by other diamonds. In particular, nanocrystalline diamond aggregates were measured to be harder than any large single crystal diamond. Those aggregates are produced by high-pressure high-temperature treatment of graphite or fullerite (C60).
source: wikipedia.org
