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In mineralogy, diamond ( or ; from the ancient Greek ἀδάμας – ''adámas'' "unbreakable") is a metastable 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 standard 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 and the scientific applications in diamond knives and diamond anvil cells. Because of its extremely rigid lattice, it can be contaminated by very few types of impurities, such as boron and nitrogen. Small amounts of defects or impurities (about one per million of lattice atoms) color diamond blue (boron), yellow (nitrogen), brown (lattice defects), green (radiation exposure), purple, pink, orange or red. Diamond also has relatively high optical dispersion (ability to disperse light of different colors). Most natural diamonds are formed at high temperature and pressure at depths of in the Earth's 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's 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 HPHT method which approximately simulates the conditions in the Earth's mantle. An alternative, and completely different growth technique is chemical vapor deposition (CVD). 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 developed to distinguish natural, synthetic diamonds and diamond simulants. ==History== The name ''diamond'' is derived from the ancient Greek ''αδάμας'' ''(adámas''), "proper", "unalterable", "unbreakable", "untamed", from ἀ- (a-), "un-" + ''δαμάω'' (''damáō''), "I overpower", "I tame".〔 〕 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 1772, Antoine Lavoisier 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.〔See: * Lavoisier (1772) ("Premier mémoire sur la destruction du diamant par le feu" ) (First memoir on the destruction of diamond by fire), ''Histoire de l'Académie royale des sciences. Avec les Mémoires de Mathématique & de Physique'' (History of the Royal Academy of Sciences. With the Memoirs of Mathematics and Physics), part 2, 564-591. * Lavoisier (1772) ("Second mémoire sur la destruction du diamant par le feu" ) (Second memoir on the destruction of diamond by fire), ''Histoire de l'Académie royale des sciences. Avec les Mémoires de Mathématique & de Physique'', part 2, 591-616.〕 Later in 1797, Smithson Tennant repeated and expanded that experiment.〔Smithson Tennant (1797) ("On the nature of the diamond," ) ''Philosophical Transactions of the Royal Society of London'', 87 : 123-127.〕 By demonstrating that burning diamond and graphite releases the same amount of gas, he established the chemical equivalence of these substances.〔 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 20th 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'' (its weight), ''cut'' (quality of the cut is graded according to proportions, symmetry and polish), ''color'' (how close to white or colorless; For fancy diamonds how intense is its hue), and ''clarity'' (how free is it from inclusions). A large, flawless diamond is known as a paragon. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「diamond」の詳細全文を読む スポンサード リンク
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