Diamond

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Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic.wikipedia
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Allotropes of carbon

allotrope of carboncarboncarbon allotrope
Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic.
Well-known forms of carbon include diamond and graphite.

Graphite

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At room temperature and pressure, another solid form of carbon known as graphite is the chemically stable form, but diamond almost never converts to it.
Under high pressures and temperatures it converts to diamond.

Diamond cubic

diamonddiamond latticediamond crystal
Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic.
While the first known example was diamond, other elements in group 14 also adopt this structure, including α-tin, the semiconductors silicon and germanium, and silicon/germanium alloys in any proportion.

Diamond simulant

imitation diamondImitation diamondsdiamond
Imitation diamonds can also be made out of materials such as cubic zirconia and silicon carbide.
A diamond simulant, diamond imitation or imitation diamond is an object or material with gemological characteristics similar to those of a diamond.

Cubic zirconia

American diamondscubiccubic form of zirconia
Imitation diamonds can also be made out of materials such as cubic zirconia and silicon carbide.
Because of its low cost, durability, and close visual likeness to diamond, synthetic cubic zirconia has remained the most gemologically and economically important competitor for diamonds since commercial production began in 1976.

Allotropy

allotropeallotropesallotropic
Solid carbon comes in different forms known as allotropes depending on the type of chemical bond.
For example, the allotropes of carbon include diamond (the carbon atoms are bonded together in a tetrahedral lattice arrangement), graphite (the carbon atoms are bonded together in sheets of a hexagonal lattice), graphene (single sheets of graphite), and fullerenes (the carbon atoms are bonded together in spherical, tubular, or ellipsoidal formations).

Engagement ring

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Unlike many other gems, it is well-suited to daily wear because of its resistance to scratching—perhaps contributing to its popularity as the preferred gem in engagement or wedding rings, which are often worn every day.
In Western countries, engagement rings are worn mostly by women, and rings can feature diamonds or other gemstones.

Lonsdaleite

Diamonds can also form an ABAB ... structure, which is known as hexagonal diamond or lonsdaleite, but this is far less common and is formed under different conditions from cubic carbon.
The great heat and stress of the impact transforms the graphite into diamond, but retains graphite's hexagonal crystal lattice.

Boron nitride

cubic boron nitridehexagonal boron nitrideBoron nitride nanotube
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 and nanocrystalline diamond aggregates.
The cubic (sphalerite structure) variety analogous to diamond is called c-BN; it is softer than diamond, but its thermal and chemical stability is superior.

Aggregated diamond nanorod

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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 and nanocrystalline diamond aggregates.
Aggregated diamond nanorods, or ADNRs, are a nanocrystalline form of diamond, also known as nanodiamond or hyperdiamond.

Facet

crystal facetsfacetedfaceting
As diamond's crystal structure has a cubic arrangement of the atoms, they have many facets that belong to a cube, octahedron, rhombicosidodecahedron, tetrakis hexahedron or disdyakis dodecahedron.
Of the hundreds of facet arrangements that have been used, the most famous is probably the round brilliant cut, used for diamond and many colored gemstones.

Thermal conductivity

heat conductivitythermalconductivity
Diamond has the highest hardness and thermal conductivity of any natural material, properties that are utilized in major industrial applications such as cutting and polishing tools.
Of all materials, allotropes of carbon, such as graphite and diamond, are usually credited with having the highest thermal conductivities at room temperature.

Metastability

metastablemetastable stateunstable molecules
At normal temperature and pressure, 20 C and 1 atm, the stable phase of carbon is graphite, but diamond is metastable and its rate of conversion to graphite is negligible.
As another example, diamond is a stable phase only at very high pressures, but is a metastable form of carbon at standard temperature and pressure.

Diamond anvil cell

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They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth.
A DAC consists of two opposing diamonds with a sample compressed between the polished culets (tips).

Blue diamond

blue diamonds
Other specialized applications also exist or are being developed, including use as semiconductors: some blue diamonds are natural semiconductors, in contrast to most diamonds, which are excellent electrical insulators.
Blue diamond is a type of diamond which exhibits all of the same inherent properties of the mineral except with the additional element of blue color in the stone.

Carbonado

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"Black", or Carbonado, diamonds are not truly black, but rather contain numerous dark inclusions that give the gems their dark appearance.
It is an impure form of polycrystalline diamond consisting of diamond, graphite, and amorphous carbon.

Vickers hardness test

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Diamond is the hardest known natural material on both the Vickers scale and the Mohs scale.
A diamond in the form of a square-based pyramid satisfied these conditions.

Nitrogen

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Because the arrangement of atoms in diamond is extremely rigid, few types of impurity can contaminate it (two exceptions being boron and nitrogen).
This structure is similar to that of diamond, and both have extremely strong covalent bonds, resulting in its nickname "nitrogen diamond".

Germanium

GeGe diodesGerman
At high pressures, silicon and germanium have a BC8 body-centered cubic crystal structure, and a similar structure is predicted for carbon at high pressures.
This form constitutes an allotrope known as α-germanium, which has a metallic luster and a diamond cubic crystal structure, the same as diamond.

Mohs scale of mineral hardness

Mohs hardnessMohs scalehardness
Diamond is the hardest known natural material on both the Vickers scale and the Mohs scale.
As the hardest known naturally occurring substance when the scale was designed, diamonds are at the top of the scale.

Detonation nanodiamond

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In addition, when meteorites strike the ground, the shock wave can produce high enough temperatures and pressures for microdiamonds and nanodiamonds to form.
Detonation nanodiamond (DND), also known as ultradispersed diamond (UDD), is diamond that originates from a detonation.

Diamantaire

diamantaires
Taken together, these factors affect the overall appearance of a polished diamond and most diamantaires still rely upon skilled use of a loupe (magnifying glass) to identify diamonds "by eye".
A diamantaire (French origin) is a gem-quality diamond manufacturer or producer, master diamond cutter, and graduate gemologist specialized in diamonds.

Bingara, New South Wales

Bingara
The hardest natural diamonds mostly originate from the Copeton and Bingara fields located in the New England area in New South Wales, Australia.
Bingara is one of the few places in Australia where diamonds have been found.

Ballas

There have been attempts to classify them into groups with names such as boart, ballas, stewartite and framesite, but there is no widely accepted set of criteria.
Ballas or shot bort is a term used in the diamond industry to refer to shards of non-gem-grade and -quality diamonds.

Carbon flaw

Most diamond impurities replace a carbon atom in the crystal lattice, known as a carbon flaw.
A carbon flaw is a blemish present within a diamond crystalline form of carbon, usually seen as a black spot.