Diamond - Wikipedia. Diamond. The slightly misshapen octahedral shape of this rough diamond crystal in matrix is typical of the mineral. Its lustrous faces also indicate that this crystal is from a primary deposit. General. Category. Native minerals. Formula(repeating unit)CStrunz classification. CB. 1. 0a. Dana classification.

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Crystal system. Cubic. Crystal class. Hexoctahedral (m. H- M symbol: (4/m 3 2/m)Identification. Formula mass. 69. Color. Typically yellow, brown, or gray to colorless. Less often blue, green, black, translucent white, pink, violet, orange, purple, and red.

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Crystal habit. Octahedral. Twinning. Spinel law common (yielding "macle")Cleavage. Fracture. Conchoidal (shell- like)Mohs scale hardness. Luster. Adamantine. Streak. Colorless. Diaphaneity. Transparent to subtransparent to translucent. Specific gravity.

Density. 3. 5–7. 00. Polish luster. Adamantine. Optical properties. Isotropic. Refractive index.

Birefringence. None. Pleochroism. None. Dispersion. 0. 0. Melting point. Pressure dependent. References[1][2]Diamond ( or ) is a metastableallotrope of carbon, where the carbonatoms 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 1. Earth's mantle. Carbon- containing minerals provide the carbon source, and the growth occurs over periods from 1 billion to 3. Earth). Diamonds are brought close to the Earth's surface through deep volcanic eruptions by 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 diamonds, synthetic diamonds, and diamond simulants. The word is from the ancient Greek ἀδάμας – adámas "unbreakable".

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".[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 3,0. 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.[5][6] The popularity of diamonds has risen since the 1. In 1. 77. 2, the French scientist 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.[8] Later in 1. English chemist Smithson Tennant repeated and expanded that experiment.[9] By demonstrating that burning diamond and graphite releases the same amount of gas, he established the chemical equivalence of these substances.[1. The most familiar uses of diamonds today are as gemstones used for adornment, a use which dates back into antiquity, and as industrial abrasives for cutting hard materials. The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds.

In the 2. 0th century, experts in gemology 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).[1. A large, flawless diamond is known as a paragon. Geology. The formation of natural diamond requires very specific conditions—exposure of carbon- bearing materials to high pressure, ranging approximately between 4.

GPa), but at a comparatively low temperature range between approximately 9. C (1,6. 50 and 2,3. F). These conditions are met in two places on Earth; in the lithospheric mantle below relatively stable continental plates, and at the site of a meteorite strike.[1. Formation in cratons.

The conditions for diamond formation to happen in the lithospheric mantle occur at considerable depth corresponding to the requirements of temperature and pressure. These depths are estimated between 1.

The rate at which temperature changes with increasing depth into the Earth varies greatly in different parts of the Earth. In particular, under oceanic plates the temperature rises more quickly with depth, beyond the range required for diamond formation at the depth required. The correct combination of temperature and pressure is only found in the thick, ancient, and stable parts of continental plates where regions of lithosphere known as cratons exist. Long residence in the cratonic lithosphere allows diamond crystals to grow larger.[1. Through studies of carbon isotope ratios (similar to the methodology used in carbon dating, except with the stable isotopes.

C- 1. 2 and C- 1. Some diamonds, known as harzburgitic, are formed from inorganic carbon originally found deep in the Earth's mantle. In contrast, eclogitic diamonds contain organic carbon from organic detritus that has been pushed down from the surface of the Earth's crust through subduction (see plate tectonics) before transforming into diamond. These two different source of carbon have measurably different 1. C: 1. 2C ratios. Diamonds that have come to the Earth's surface are generally quite old, ranging from under 1 billion to 3. This is 2. 2% to 7. Earth.[1. 3]Transport from mantle.

Schematic diagram of a volcanic pipe. Diamond- bearing rock is carried from the mantle to the Earth's surface by deep- origin volcanic eruptions. The magma for such a volcano must originate at a depth where diamonds can be formed[1. This is a relatively rare occurrence. These typically small surface volcanic craters extend downward in formations known as volcanic pipes.[1.

The pipes contain material that was transported toward the surface by volcanic action, but was not ejected before the volcanic activity ceased. During eruption these pipes are open to the surface, resulting in open circulation; many xenoliths of surface rock and even wood and fossils are found in volcanic pipes. Diamond- bearing volcanic pipes are closely related to the oldest, coolest regions of continental crust (cratons). This is because cratons are very thick, and their lithospheric mantle extends to great enough depth that diamonds are stable.

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