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Diamond

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The hardest known mineral, diamond is pure carbon. Its crystals typically occur as octahedrons and cubes with rounded edges and slightly convex faces. Crystals may be transparent, translucent, or opaque. They range from colorless to black, with brown and yellow being the most common colors. Other forms include bort or boart (irregular or granular black diamond) and carbonado (microcrystalline masses). Colorless gemstones are most often used in jewelry. Most diamonds come from two rare volcanic rocks—lamproite and kimberlite. The diamonds crystallize in Earth’s mantle, generally more than 95 miles (150 km) deep, and are formed up to Earth‘s surface through volcanism. Diamonds are also found in sediment deposited by rivers or melting glaciers.

Association: Forsterite, phlogopite, pyrope, diopside, ilmenite (kimberlite pipes); ilmenite, garnet, rutile, brookite, anatase, hematite, magnetite, tourmaline, gold, zircon, topaz (placers).

Chemical Properties of Diamond

Chemical Classification Native minerals
Chemical Composition C

Physical Properties of Diamond

Color Colorless, pale yellow to deep yellow, brown, white, blue-white; less commonly in oranges, pinks, greens, blues, reds, gray to black.
Streak Colorless
Luster Adamantine to greasy
Transparency Transparent, Translucent, Opaque
Cleavage 111 perfect in four directions
Diaphaneity Transparent to subtransparent to translucent
Mohs Hardness 10
Specific Gravity 3.52±0.01
Diagnostic Properties Hardness, heat conductivity, crystal form, index of refraction, dispersion.
Crystal System Isometric
Tenacity Brittle
Fracture Irregular/Uneven
Density 3.5 – 3.53 g/cm3 (Measured)    3.515 g/cm3 (Calculated)

Optical Properties of Diamond

Type Isotropic
Color / Pleochroism Non-pleochroic
Twinning Spinel law common (yielding “macle”)
Birefringence Isotropic minerals have no birefringence
Relief Moderate

Occurrence

Primarily formed in pipes, less commonly in dikes, of deep-seated, igneous origin, composed of kimberlite or lamproite, and in alluvial deposits formed by their weathering. In carbonaceous achondrite and iron meteorites; may be formed by impact.

Uses Area

Industrial diamonds

Industrial diamonds are synthetically produced or removed from natural deposits. It is used as a cutter for industrial use. Generally, industrial diamonds are irregularly shaped and defective.They are very important in modern metal processing and mining.They are naturally found in three varieties. These are balas, bort and Karbonado.

Balas consist of spherical masses of small diamond crystals. Balas is extremely hard, hard and difficult to separate. The main sources are Brazil and South Africa. Brazilian honey is said to be more difficult.

Bort is a gray to black large diamond caused by inclusions and impurities. The drilling bore consists of an average of 20 average round stones and is used on diamond drill bits. Crushing steel, the lowest grade diamond, is crushed in steel mortars and classified into abrasive stones of various sizes; 75 percent of the world’s breaking bordu comes from the Congo. Its main use is in the manufacture of grinding wheels for sharpening cemented carbide metal cutting tools, but also used as loose grains in oil or water suspended for lapping and polishing.

Carbonado, known commercially as carbon, is black opaque diamond. It is hard as crystallized diamond but less brittle and has a lower specific gravity (3,51 to 3,29) as its structure is slightly porous. Carbonado has no release properties and is therefore valuable for use in diamond tools. It is generally seen in small masses in shiny pebbles in Bahia, Brazil and Borneo, but is also found in the Central African Republic and Siberia. Rock core drills, which are widely used in the exploration of new mineral deposits, are made by assembling diamonds around a hollow metal drill head.

Diamon is a Gemstone

The most popular stone diamond in the world. It reflects a high percentage of the light on it. As white light passes through a diamond, this high dispersion causes that light to fall into component colors. Dispersion is what enables prism to separate the white light into the colors of the spectrum.

Distribution

Numerous occurrences world-wide, but only a few are of economic importance. Formerly important deposits were

  • in India, in the Golconda region, and near Nagpur and Bundelkhand.
  • From the area around Diamantina, Minas Gerais, and other states in Brazil.
  • In South Africa, formerly obtained from the Orange and Vaal Rivers; still from along the coast north into Namibia, with offshore reserves estimated at 3 Bct.
  • Important current alluvial production from Lunda Norte Province, Angola; southeastern Sierra Leone; also from Bakwanga and Tchikapa, Kasai Province, Congo (Zaire).
  • From South Africa, in several pipes around Kimberley, at the Finsch mine, near Postmasburg, Cape Province; from the Premier mine, near Pretoria, and the Venetia mine, Transvaal; about 150 diamondiferous pipes have been mined.
  • From the Jwaneng and Orapa pipes, Botswana.
  • In Russia, in Sakha, from the Mir (Peace), Udatchnaya (Success), Zarnitsa (Thunderflash), Aikhal (Glory), and Jubileynaya (Jubilee) pipes.
  • In China, from pipes at the Wafangdian and Binhai mine, Liaoning Province; at Changma, near Mengyin, Shandong Province. Prolific production from the Argyle pipe, Kimberley, Western Australia.
  • At the Ekati and Diavik mines, Lac de Gras region, Northwest Territories, Canada.

References

  • Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
  • Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
  • Mindat.org. (2019). Diamond: Mineral information, data and localities.. [online] Available at: https://www.mindat.org/min-727.html [Accessed 4 Mar. 2019].

Cite this article as: Geology Science. (2019). Diamond. [online] Available at: http://geologyscience.com/minerals/diamond/ [5th December 2019 ]
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