صور الالماس الخام في الطبيعة بالمكروسكوب

A rough diamond is a diamond rock which has not been cut or processed. They come in a variety of naturally occurring shapes including octahedrons (eight sided bi-pyramid), cubic and triangular (most commonly macles). Bort, boart, or boort is an umbrella term used in the diamond industry to refer to shards of non-gem-grade/quality diamonds. In the manufacturing and heavy industries, "bort" is used to describe dark, imperfectly formed or crystallized diamonds of varying levels of opacity. The lowest grade, "crushing bort," is crushed by steel mortars and used to make industrial-grade abrasive grits. Small bort crystals are used in drill bits. The Carbonado, commonly known as black diamond, is the toughest form of natural diamond. It is an impure form of polycrystalline diamond consisting of diamond, graphite, and amorphous carbon.[1] It is found primarily in alluvial deposits in the Central African Republic and in Brazil. Its natural colour is black or dark grey, and it is more porous than other diamonds. Contents 1 Unusual properties 2 Theories on origin 2.1 Extraterrestrial origin hypothesis 3 See also 4 References 5 External links Unusual properties Carbonado diamonds are typically pea-sized or larger porous aggregates of many tiny black crystals. The most characteristic carbonados have been found only in the Central African Republic and in Brazil, in neither place associated with kimberlite, the source of typical gem diamonds. Lead isotope analyses have been interpreted as documenting crystallization of carbonados about 3 billion years ago. The carbonados are found in younger sedimentary rocks.[2] Mineral grains included within diamonds have been studied extensively for clues to diamond origin. Some typical diamonds contain inclusions of common mantle minerals such as pyrope and forsterite, but such mantle minerals have not been observed in carbonado. In contrast, some carbonados contain inclusions of minerals characteristic of the Earth's crust; the inclusions do not necessarily establish formation of the diamonds in the crust, but because while the obvious crystal inclusions occur in the pores that are common in carbonados, they may have been introduced after carbonado formation. Inclusions of other minerals, rare or nearly absent in the Earth's crust, are found at least partly incorporated in diamond, not just in pores: among such other minerals are those with compositions of Si, SiC, and Fe‑Ni. No distinctive high-pressure minerals, including the hexagonal carbon polymorph, lonsdaleite, have been found as inclusions in carbonados although such inclusions might be expected if carbonados formed by meteorite impact.[2] Isotope studies have yielded further clues to carbonado origin. The carbon isotope value is very low (little carbon‑13 compared to carbon‑12, relative to typical diamonds).[2] Carbonado exhibits strong luminescence (photoluminescence and cathodoluminescence) induced by nitrogen and by vacancies existing in the crystal lattice. Luminescence halos are present around radioactive inclusions, and it is suggested that the radiation damage occurred after formation of the carbonados,[3] an observation perhaps pertinent to the radiation hypothesis listed below.Democratic Republic of the Congo provides 75% of the world supply of crushing bort.[1][2][3] Use and application Apart from the use of bort in the diamond gem industry, where the material is used as an abrasive —with a hardness close to or the same as that of diamond itself— to scour and polish the various facets of gem stones, in smaller flakes and particles it is also used as an additive for scouring or polishing pastes and agents. Larger particles find their use as a protective and cutting edge to drill bits, saws and other (cutting) tools and machinery for longer lifespan and to substantially increase their efficiency (for instance, for tools that drill or saw through (reinforced) concrete —cement, stone (pebbles) and steel (rebar) alike— or other hard materials, both metal and non-metal).[4] When bort particles varying from one to two nanometers[5] are added to lubricants such as paraffin oil, these particles will embed themselves into minute irregularities and imperfections of moving-part surfaces, whereas particles that remain suspended in the lubricant oil act as both a polishing agent further smoothening the surfaces, as well as ball bearings between the surfaces that move relative to or revolve within or around one another. Such nanotechnology applications with paraffin oil containing approximately 1% of these nano-size bort particles may decrease the friction up to half of that without the nano-particles.[6][7] See also icon Geology portal Minerals portal Look up bort in Wiktionary, the free dictionary. Carbonado (black diamond) Synthetic diamond Ballas References See also Bort Carbonado Diamond clarity Diamond type

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