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

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At room temperature and pressureanother solid form of carbon known as graphite is the chemically stable form, but diamond almost never converts to it.

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.

They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth. Because the arrangement of atoms in diamond is extremely rigid, few types of impurity can contaminate it two exceptions being boron and nitrogen.

Small numbers of defects or impurities about one per million of lattice atoms color diamond blue boronyellow nitrogenbrown defectsgreen radiation exposurepurple, pink, orange or red.

Diamond also has relatively high optical dispersion ability to disperse light of different colors. Under high pressure and temperature, carbon-containing fluids dissolved minerals and replaced them with diamonds.

Much more recently tens to hundreds of million years agothey were carried to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites.

Synthetic diamonds can be grown from high-purity carbon under high pressures and temperatures or from hydrocarbon gas by chemical vapor deposition CVD.

Imitation diamonds can also be made out of materials such as cubic zirconia and silicon carbide.

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Natural, synthetic and imitation diamonds are most commonly distinguished using optical techniques or thermal conductivity measurements. Diamond is a solid form of pure carbon with its atoms arranged in a crystal.

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Solid carbon comes in different forms known as allotropes depending on the type of chemical bond. The two most common allotropes of pure carbon are diamond and graphite.

In graphite the bonds are sp 2 orbital hybrids and the atoms form in planes with each bound to three nearest neighbors degrees apart.

In diamond they are sp 3 and the atoms form tetrahedra with each bound to four nearest neighbors. Thus, graphite is much softer than diamond. However, the stronger bonds make graphite less flammable.

Diamonds have been adapted for many uses because of the material’s exceptional physical characteristics. Of all known substances, it is the hardest and least compressible.

It has the highest thermal conductivity and the highest sound velocity. It has low adhesion and friction, and its coefficient of thermal expansion is extremely low.

Its optical transparency extends from the far infrared to the deep ultraviolet and it has high optical dispersion. It also has high electrical resistance.

It is chemically inert, not reacting with most corrosive substances, and has excellent biological compatibility.

The equilibrium pressure and temperature conditions for a transition between graphite and diamond is well established theoretically and experimentally.

The pressure changes linearly between 1. Above the triple point, the melting point of diamond increases slowly with increasing pressure; but at pressures of hundreds of GPa, it decreases.

The most common crystal structure of diamond is called diamond cubic. It is formed of unit cells see the figure stacked together.

Although there are 18 atoms in the figure, each corner atom is shared by eight unit cells and each atom in the center of a face is shared by two, so there are a total of eight atoms per unit cell.

Diamonds can also form an ABAB Diamonds occur most often as euhedral or rounded octahedra and twinned octahedra known as macles. As diamond’s crystal structure has a cubic arrangement of the atoms, they have many facets that belong to a cubeoctahedron, rhombicosidodecahedrontetrakis hexahedron or disdyakis dodecahedron.

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The crystals can have rounded off and unexpressive edges and can be elongated. Diamonds especially those with rounded crystal faces are commonly found coated in nyfan opaque gum-like skin.

Some diamonds have opaque fibers.

As the pressure decreases, a vapor phase exsolves from the magma, and this helps to keep the magma fluid. white gold wedding bands for women 14k It was sold for

They are referred to as opaque if the fibers grow from a clear substrate or fibrous if they occupy the entire crystal. Their colors range from yellow to green or gray, sometimes with cloud-like white to gray impurities.

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Their most common shape is cuboidal, but they can also form octahedra, dodecahedra, macles or combined shapes. The structure is the result of numerous impurities with sizes between 1 and 5 microns.

These diamonds probably formed in kimberlite magma and sampled the volatiles. Diamonds can also form polycrystalline aggregates. There have been attempts to classify them into groups with names such as boartballasstewartite and framesite, but there is no widely accepted set of criteria.

There are many theories for its origin, including formation in a star, but no consensus. Diamond is the hardest known natural material on both the Vickers scale and the Mohs scale.

Diamond’s great hardness relative to other materials has been known since antiquity, and is the source of its name. The hardness of diamond contributes to its suitability as a gemstone.

Because it can only be scratched by other diamonds, it maintains its polish extremely well. 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 ringswhich are often worn every day.

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These diamonds are generally small, perfect to semiperfect octahedra, and are used to polish other diamonds. Their hardness is associated with the crystal growth form, which is single-stage crystal growth.

Most other diamonds show more evidence of multiple growth stages, which produce inclusions, flaws, and defect planes in the crystal lattice, all of which affect their hardness.

It is possible to treat regular diamonds under a combination of high pressure and high temperature to produce diamonds that are harder than the diamonds used in hardness gauges.

Somewhat related to hardness is another mechanical property toughnesswhich is a material’s ability to resist breakage from forceful impact.

The toughness of natural diamond has been measured as 7.

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As with any material, the macroscopic geometry of a diamond contributes to its resistance to breakage. Diamond has a cleavage plane and is therefore more fragile in some orientations than others.

Diamond cutters use this attribute to cleave some stones, prior to faceting. Usually, attempting to deform bulk diamond crystal by tension or bending results in brittle fracture.

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.

Boron substitutes for carbon atoms in the diamond lattice, donating a hole into the valence band. Substantial conductivity is commonly observed in nominally undoped diamond grown by chemical vapor deposition.

This conductivity is associated with hydrogen-related species adsorbed at the surface, and it can be removed by annealing or other surface treatments.

Diamonds are naturally lipophilic and hydrophobicwhich means the diamonds’ surface cannot be wet by water, but can be easily wet and stuck by oil.

This property can be utilized to extract diamonds using oil when making synthetic diamonds. However, when diamond surfaces are chemically modified with certain ions, they are expected to become so hydrophilic that they can stabilize multiple layers of water ice at human body temperature.

The surface of diamonds is partially oxidized. The oxidized surface can be reduced by heat treatment under hydrogen flow.

That is to say, this heat treatment partially removes oxygen-containing functional groups. The structure gradually changes into sp 2 C above this temperature.

Thus, diamonds should be reduced under this temperature. At room temperature, diamonds do not react with any chemical reagents including strong acids and bases.

It increases in temperature from red to white heat and burns with a pale blue flame, and continues to burn after the source of heat is removed.

By contrast, in air the combustion will cease as soon as the heat is removed because the oxygen is diluted with nitrogen. A clear, flawless, transparent diamond is completely converted to carbon dioxide; any impurities will be left as ash.

Jewelers must be careful when molding the metal in a diamond ring.

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Diamond powder of an appropriate grain size around 50 microns burns with a shower of sparks after ignition from a flame.

Consequently, pyrotechnic compositions based on synthetic diamond powder can be prepared. The resulting sparks are of the usual red-orange color, comparable to charcoal, but show a very linear trajectory which is explained by their high density.

Diamond has a wide bandgap of 5. This means that pure diamond should transmit visible light and appear as a clear colorless crystal.

Colors in diamond originate from lattice defects and impurities. The diamond crystal lattice is exceptionally strong, and only atoms of nitrogenboron and hydrogen can be introduced into diamond during the growth at significant concentrations up to atomic percents.

Transition metals nickel and cobaltwhich are commonly used for growth of synthetic diamond by high-pressure high-temperature techniques, have been detected in diamond as individual atoms; the maximum concentration is 0.

Virtually any element can be introduced to diamond by ion implantation. Nitrogen is by far the most common impurity found in gem diamonds and is responsible for the yellow and brown color in diamonds.

Boron is responsible for the blue color. Plastic deformation is the cause of color in some brown [45] and perhaps pink and red diamonds. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless.

Most diamond impurities replace a carbon atom in the crystal latticeknown as a carbon flaw. The most common impurity, nitrogen, causes a slight to intense yellow coloration depending upon the type and concentration of nitrogen present.

Diamonds of a different color, such as blue, are called fancy colored diamonds and fall under a different grading scale. Inthe Wittelsbach Diamonda Their high refractive index is also indicative, but other materials have similar refractivity.

Diamonds cut glass, but this does not positively identify a diamond because other materials, such as quartz, also lie above glass on the Mohs scale and can also cut it.

Diamonds can scratch other diamonds, but this can result in damage to one or both stones. Hardness tests are infrequently used in practical gemology because of their potentially destructive nature.