This article addresses the material properties of diamond. For a broader discussion of diamonds, see diamond. For other uses of the word diamond, see diamond (disambiguation). A scattering of round-brilliant cut diamonds shows off the many reflecting facets. ... Diamond is: the name of a form of carbon valued for its beauty in jewelry and its hardness in industrial uses; a square or rhombus whose longest diagonal is usually aligned vertically; the shape of a 2-polyiamond; a playing card marked with a stylized red diamond (), or when plural...

Diamond
An octahedral diamond crystal in matrix.
General
Category	Native Nonmetal, Mineral
Formula	Carbon, C
Identification
Color	Most often colorless to yellow or brown. Rarely pink, orange, green or blue.
Habit	Octahedral, spherical or massive
System	Isometric
Cleavage	Octahedral; perfect and easy
Fracture	Conchoidal
Hardness	10
Luster	Adamantine to greasy
RI	2.417
Pleochroism	None
Streak	None
SG	3.516 - 3.525
Fusibility	Burns above 800°C
Solubility	Resistant to acids
Major varieties
Ballas	Spherical, radial structure, cryptocrystalline, opaque black
Bort	Poorly-formed, cryptocrystalline, shapeless, translucent
Carbonado	Massive, microcrystalline, opaque black

Diamond is transparent to opaque, optically isotropic crystalline carbon. It is the hardest naturally-occurring material known—owing to its strong covalent bonding—yet its toughness is only fair to good due to important structural weaknesses. Diamond has a high refractive index (2.417) and moderate dispersion (0.044), properties which are considered carefully during diamond cutting and which (together with their hardness) give cut diamonds their brilliance and fire. Scientists classify diamonds into two main types and several subtypes, depending on the nature of crystallographic defects present. Trace impurities substitutionally replacing carbon atoms in a diamond's crystal lattice, and in some cases structural defects, are responsible for the wide range of colors seen in diamond. Most diamonds are electrical insulators but extremely efficient thermal conductors. The specific gravity of single-crystal diamond (3.52) is fairly constant. Contrary to a common misconception, diamond is not the most stable form of solid carbon; graphite has that distinction. Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... This article is about minerals in the geologic sense; for nutrient minerals see dietary mineral; for the band see Mineral (band). ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... In mineralogy, shape and size give rise to descriptive terms applied to the typical appearance, or habit of crystals. ... In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... In crystallography, the cubic crystal system (or isometric crystal system) is the most symmetric of the 7 crystal systems. ... Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. ... For fractures in bones, see Fracture (bone). ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ... Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ... The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ... Pleochroism is an optical phenomenon where due to double refraction of light by a colored gem or crystal, the light is divided into two paths which are polarized at a 90° angle to each other. ... The term streak is used in several ways: Streaking, the act of running around nude in public places. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... Fusibility is the ease with which a material will melt. ... A substance is soluble in a fluid if it dissolves in that fluid. ... Grand Theft Auto: San Andreas is the sixth video game in the Grand Theft Auto series. ... For the fictional word, see Made_up words in The Simpsons. ... Carbonado is a natural polycrystalline diamond found in alluvial deposits in the Central African Republic and Brazil. ... Isotropic means independent of direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... In materials science, hardness is the characteristic of a solid material expressing its resistance to permanent deformation. ... Covalently bonded hydrogen and carbon in a molecule of methane. ... Toughness, in material science and metallurgy, is the resistance to fracture of a material when suddenly stressed. ... The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ... Dispersion of a light beam in a prism. ... Diamond Cutting is the art, skill and, increasingly, science of changing a diamond from a rough stone into an attractive gem. ... Crystalline solids have a very regular atomic structure: that is, the local positions of atoms with respect to each other are repeated at the atomic scale. ... In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... // Definition An Insulator is a material or object which resists the flow of electric charge. ... In physics, thermal conductivity, λ or k, is the intensive property of a material which relates its ability to conduct heat. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... Graphite (named by Abraham Gottlob Werner in 1789, from the Greek γραφειν: to draw/write, for its use in pencils) is one of the allotropes of carbon. ...

Hardness and crystal structure

See also: Crystallographic defects in diamond This article addresses the possible defects of a diamond crystal. ...

Known to the Ancient Greeks as adamas ("untameable" or "unconquerable") and sometimes called adamant, diamond is the hardest known naturally occurring material, scoring 10 on the old Mohs scale of mineral hardness. The material boron nitride, when in a form structurally identical to diamond, is nearly as hard as diamond; a currently hypothetical material, beta carbon nitride, may also be as hard or harder in one form. Furthermore, it has been shown 1 2 that ultrahard fullerite (C⁶⁰) (not to be confused with P-SWNT Fullerite) when testing diamond hardness with a scanning force microscope can scratch diamond. In turn, using more accurate measurments, these values are now known for diamond hardness. A Type IIa diamond (111) has a hardness value of 167 GPa (±6) when scratched with an ultrahard fullerite tip. A Type IIa diamond (111) has a hardness value of 231 GPa (±5) when scratched with a diamond tip which leads to hypothetically inflated values. Note: This article contains special characters. ... Look up Adamant in Wiktionary, the free dictionary Adamant and similar words are used to refer to any especially hard substance, whether composed of diamond, some other gemstone, or some type of metal. ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ... Boron nitride is a binary chemical compound, consisting of equal proportions of boron and nitrogen, with formula BN. Structurally, it is isoelectronic to carbon and takes on similar physical forms: a hexagonal, graphite-like one, and a cubic, diamond-like one. ... A diagram of (β-C3N4) Beta carbon nitride (β-C3N4) is a theoretical material, derived from theories on crystalline structure. ... Scratch caused by ultrahard fullerite on diamond Ultrahard fullerite (C60) is a form of carbon found to be harder than diamond, and which can be used to create even harder materials, such as aggregated diamond nanorods. ... Fullerites, or Polymerized Single Walled NanoTubules (P-SWNT) are very hard like diamond, but because the nanotubules intertwine they dont have the corresponding crystal lattice that makes it possible to cut diamonds neatly. ... The atomic force microscope (AFM) is a very powerful microscope invented by Binnig, Quate and Gerber in 1986. ... The pascal (symbol Pa) is the SI unit of pressure. ... Scratch caused by ultrahard fullerite on diamond Ultrahard fullerite (C60) is a form of carbon found to be harder than diamond, and which can be used to create even harder materials, such as aggregated diamond nanorods. ... The pascal (symbol Pa) is the SI unit of pressure. ...

The diamond crystal bond structure gives the gem its hardness and differentiates it from graphite.

Cubic diamonds have a perfect and easy octahedral cleavage, which means that they have four planes—directions following the faces of the octahedron where there are fewer bonds and therefore points of structural weakness—along which diamond can easily split (following a blunt impact), leaving smooth surfaces. Similarly, diamond's hardness is markedly directional: the hardest direction is the diagonal on the cube face, 100 times harder than the softest direction, which is the dodecahedral plane. The octahedral plane, followed by the axial directions on the cube plane, are intermediate between the two extremes. The diamond cutting process relies heavily on this directional hardness, as without it a diamond would be nearly impossible to fashion. Cleavage also plays a helpful role, especially in large stones where the cutter wishes to remove flawed material or to produce more than one stone from the same piece of rough. Diamond Crystal Bond Structure - model built and photographed by Vincent Herr 2001. ... In materials science, hardness is the characteristic of a solid material expressing its resistance to permanent deformation. ... Graphite (named by Abraham Gottlob Werner in 1789, from the Greek γραφειν: to draw/write, for its use in pencils) is one of the allotropes of carbon. ... An octahedron (plural: octahedra) is a polyhedron with eight faces. ... Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. ... A cube (or regular hexahedron) is a three-dimensional Platonic solid composed of six square faces, with three meeting at each vertex. ... A dodecahedron is literally a polyhedron with 12 faces, but usually a regular dodecahedron is meant: a Platonic solid composed of twelve pentagonal faces, with three meeting at each vertex. ... Diamond Cutting is the art, skill and, increasingly, science of changing a diamond from a rough stone into an attractive gem. ... Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. ...

Diamonds typically crystallize in the cubic crystal system and consist of tetrahedrally, covalently bonded carbon atoms. A second form called lonsdaleite with hexagonal symmetry is also found, but it is extremely rare and is believed to form only when meteoric graphite falls to Earth. The local environment of each atom is identical in the two structures. In terms of crystal habit, diamonds occur most often as euhedral (well-formed) or rounded octahedra and twinned, flattened octahedra known as macles (with a triangular outline). Other forms include dodecahedra and (rarely) cubes. There is some evidence that interstitial nitrogen impurities play an important role in the formation of euhedral crystals—the largest diamonds found, such as the Cullinan Diamond, have been shapeless or massive. These diamonds are Type II and therefore contain little if any nitrogen (see Composition and color). In crystallography, the cubic crystal system (or isometric crystal system) is the most symmetric of the 7 crystal systems. ... In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... For academic journal, see Tetrahedron A tetrahedron (plural: tetrahedra) is a polyhedron composed of four triangular faces, three of which meet at each vertex. ... Covalently bonded hydrogen and carbon in a molecule of methane. ... Lonsdaleite is a hexagonal polymorph of the carbon allotrope diamond, believed to form when meteoric graphite falls to Earth. ... In crystallography, the hexagonal crystal system is one of the 7 lattice point groups. ... A burst of meteors A meteor is the visible path of a meteoroid that enters the Earths (or another bodys) atmosphere, commonly called a shooting star or falling star. ... Graphite (named by Abraham Gottlob Werner in 1789, from the Greek γραφειν: to draw/write, for its use in pencils) is one of the allotropes of carbon. ... Earth, also known as Terra, and Tellus mostly in the 19th century, is the third-closest planet to the Sun. ... In mineralogy, shape and size give rise to descriptive terms applied to the typical appearance, or habit of crystals. ... Euhedral refers to well formed crystals with sharp easily recognised faces. ... A twin boundary occurs when two crystals of the same type intergrow, so that only a slight misorientation exists between them. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... The Cullinan Diamond, found by Frederick Wells, surface manager of the Premier Diamond Mining Company in Cullinan, Gauteng, South Africa on June 25 1905, is the largest rough gem-quality diamond ever found, at 3,106. ...

The faces of diamond octahedrons are highly lustrous due to their hardness; growth defects in the form of trigons or etch pits are often present on the faces, the former being triangular pits whose points are aligned with the faces of the octahedron. A diamond's fracture may be step-like, conchoidal (shell-like, similar to glass) or irregular. Diamonds which are nearly round due to the stepping tendency of octahedrons are commonly found coated in nyf, a gum-like skin; the combination of stepped faces, growth defects, and nyf produces a "scaly" or corrugated appearance, and such diamonds are termed crinkles. A significant number of diamonds crystallize anhedrally: that is, their forms are so distorted that few crystal faces are discernable. Some diamonds found in Brazil and the Democratic Republic of the Congo are cryptocrystalline and occur as opaque, darkly-colored, spherical, radial masses of tiny crystals; these are known as ballas and are important to industry as they lack the cleavage planes of single-crystal diamond. Carbonado is a similar opaque microcrystalline form which occurs in shapeless masses. Like ballas diamond, carbonado lacks cleavage and its specific gravity varies widely, from 2.9–3.5. Bort diamonds, found in Brazil, Venezuela, and Guyana, are the most common type of industrial-grade diamond, also cryptocrystalline or otherwise poorly crystallized, but possessing cleavage, translucency, and lighter colors. Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ... The term Trigon may refer to several things: A three-sided ancient Greek or Roman lyre. ... For fractures in bones, see Fracture (bone). ... Conchoidal fracture describes the way that brittle materials break when they do not follow any natural planes of separation. ... This article refers to the material. ... A cryptocrystal is a rock whose texture is so finely crystalline—that is, made up of such minute crystals—that its crystalline nature is only vaguely revealed even in a thin section by transmitted polarized light. ... Grand Theft Auto: San Andreas is the sixth video game in the Grand Theft Auto series. ... Carbonado is a natural polycrystalline diamond found in alluvial deposits in the Central African Republic and Brazil. ... For the fictional word, see Made_up words in The Simpsons. ...

Due to its great hardness and strong molecular bonding, a cut diamond's facets and facet edges are observably the flattest and sharpest. A curious side effect of diamond's surface perfection is hydrophobia combined with lipophilia. The former property means a drop of water placed on a diamond will form a coherent droplet, whereas in most other minerals the water would spread out to cover the surface. Similarly, diamond is unusually lipophilic, meaning grease and oil readily collect on a diamond's surface. Whereas on other minerals oil would form coherent drops, on a diamond the oil would spread. This property is exploited in the use of so-called "grease pens," which apply a line of grease to the surface of a suspect diamond simulant. Facets are flat faces on geometric shapes. ... The word grease can mean:- A type of industrial lubricant: see grease (lubricant). ... Oil is a generic term for organic liquids that are not miscible with water. ... This article addresses the many imitations of diamond. ...

Toughness

Unlike hardness, which only denotes resistance to scratching, diamond's toughness or tenacity is only fair to good. Toughness relates to its ability to resist breakage from falls or impacts: due to diamond's perfect and easy cleavage, it is vulnerable to breakage. Ballas and carbonado diamond are exceptional, as they are polycrystalline and therefore much tougher than single-crystal diamond; they are used for deep-drilling bits and other demanding industrial applications. Particular cuts of diamonds are more prone to breakage—such as marquis or other cuts featuring tapered points—and thus may be uninsurable by reputable insurance companies. The culet is a facet (parallel to the table) given to the pavilion of cut diamonds designed specifically to reduce the likelihood of breakage or splintering. Extremely thin, or very thin girdles are also prone to much higher breakage. Toughness, in material science and metallurgy, is the resistance to fracture of a material when suddenly stressed. ...

Solid foreign crystals are commonly present in diamond—these and other inclusions, such as internal fractures or "feathers"—can compromise the structural integrity of a diamond. Cut diamonds that have been enhanced to improve their clarity via glass infilling of fractures or cavities are especially fragile, as the glass will not stand up to ultrasonic cleaning or the rigors of the jeweler's torch. Fracture-filled diamonds may shatter if treated improperly. This article addresses treatments designed to enhance the gemological characteristics of diamond. ... Diamond clarity is a quality of diamonds relating to the existence and visual appearance of internal defects of a diamond called inclusions, and surface defects called blemishes. ... A baby in its mothers womb, viewed in a sonogram Ultrasound is sound with a frequency greater than the upper limit of human hearing, approximately 20 kilohertz/20,000 Hertz. ...

Optical properties

The luster of a diamond is described as adamantine, which simply means diamond-like. It is the highest luster possible bar that of metal (metallic), and is due to diamond's superlative hardness. Reflections on a properly cut diamond's facets are undistorted, due to their flatness. The refractive index of diamond (as measuried via sodium light, 589.3 nm) is 2.417; because it is cubic in structure, diamond is also isotropic. Its high dispersion of 0.044 (B-G interval) manifests in the perceptible fire of cut diamonds. This fire—flashes of prismatic colors seen in transparent stones—is perhaps diamond's most important optical property from a jewelry perspective. The prominence or amount of fire seen in a stone is heavily influenced by the choice of diamond cut and its associated proportions (particularly crown height), although the body color of fancy diamonds may hide their fire to some degree. For the file system called Lustre, see Lustre (file system) Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ... The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ... A sodium vapor lamp is a gas discharge lamp which uses sodium in an excited state to produce light. ... Isotropic means independent of direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented. ... Dispersion of a light beam in a prism. ... If a shaft of light entering a prism is sufficiently small such that the coloured edges meet, a spectrum results In optics, a prism is a device used to refract light, reflect it or break it up (to disperse it) into its constituent spectral colours (colours of the rainbow). ... This article addresses the many styles of diamond cut. ...

Some diamonds exhibit fluorescence of various colors and intensities under long wave (LW) ultra-violet light (365 nm): Cape series stones (Type Ia; see Composition and color) usually fluoresce blue, and these stones may also phosphoresce yellow. (This is a unique property among gemstones). Other LW flurescence colors possible are green (usually in brown stones), yellow, mauve, or red (Type IIb). In natural diamonds there is typically little if any response to shortwave (SW) ultraviolet, but the reverse is true of synthetics. Some natural Type IIb diamonds may phosphoresce blue after exposure to SW ultraviolet. In naturals, fluorescence under X-rays is generally bluish-white, yellowish or greenish. Some diamonds, particularly Canadian diamonds, show no fluorescence. Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... Phosphorescent powder under visible light, ultraviolet light, and total darkness. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz...

Cape series diamonds have a visible absorption spectrum (as seen through a direct-vision spectroscope) consisting of a fine line in the violet at 415.5 nm—however, this line is often invisible until the diamond has been cooled to very low temperatures. Colored stones show additional bands: brown diamonds show a band in the green at 504 nm, sometimes accompanied by two additional weak bands also in the green. Type II diamonds may absorb in the far red, but otherwise show no observable visible absorption spectrum. Electromagnetic radiation may be characterised by its wavelength. ... A spectroscope is a device which measures the spectrum of light. ... To help compare different orders of magnitude this page lists lengths between 100 nm and 1 µm (10-7 and 10-6 m). ...

Gemological laboratories, such as the Adamas Gemological Laboratory[1], make use of spectrophotometer machines that can distinguish natural, artificial, and color-enhanced diamonds. The spectrophotometers analyze the infrared, visible, and ultraviolet absorption spectrums of diamonds cooled with liquid nitrogen to detect tell-tale absorption lines that are not normally discernable. Gemology (gemmology outside the United States) is the science, art and profession of identifying and evaluating gemstones. ... In physics, spectrophotometry is the quantitative study of spectra. ... This article addresses treatments designed to enhance the gemological characteristics of diamond. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. ... General Name, Symbol, Number Nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15 (VA), 2 , p Density 1. ...

Electrical properties

Except for most natural blue diamonds—which are semiconductors due to substitutional boron impurities replacing carbon atoms—diamond is a good electrical insulator. Natural blue diamonds recently recovered from the Argyle diamond mine in Australia have been found to owe their color to an overabundance of hydrogen atoms: these diamonds are not semiconductors. Natural blue diamonds containing boron and synthetic diamonds doped with boron are p-type semiconductors. If an n-type semiconductor can be synthesized, electronic circuits could be manufactured from diamond. Worldwide research is in progress, with occasional successes reported, but nothing definite. In 2002 it was reported in the journal Nature that researchers have succeeded in depositing a thin diamond film on a diamond surface which is a major step towards manufacture of a diamond chip. In 2003 it was reported that NTT developed a diamond semiconductor device[2]. In April of 2004 Nature reported that below the superconducting transition temperature 4 K, boron-doped diamond synthesized at high temperature and high pressure is a bulk, type-II superconductor[3]. In October of 2004 superconductivity was found to occur in heavily boron-doped microwave plasma-assisted chemical vapor deposition (MPCVD) diamond below the superconducting transition temperature of 7.4 K[4]. A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... General Name, Symbol, Number boron, B, 5 Chemical series metalloids Group, Period, Block 13, 2, p Appearance black/brown Atomic mass 10. ... // Definition An Insulator is a material or object which resists the flow of electric charge. ... The Argyle diamond mine is very fat and stupid and you are ugly and is a diamond mine located in Australia. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... A dopant is an impurity element added to a semiconductor lattice in quite low concentrations in order to alter the optical/electrical properties of the semiconductor. ... A P-type semiconductor is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order to increase the number of free (in this case positive) charges. ... An N-type semiconductor is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order to increase the number of free (in this case negative) charge carriers. ... 2002 (MMII) was a common year starting on Tuesday of the Gregorian calendar. ... Nature is one of the oldest and most reputable scientific journals, first published on 4 November 1869. ... 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... Nippon Telegraph and Telephone (日本電信電話 Nippon Denshin Denwa) is a telephone company that dominates the telecommunication market in Japan. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Nature is one of the oldest and most reputable scientific journals, first published on 4 November 1869. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ...

Thermal properties

Unlike most electrical insulators, diamond is a good conductor of heat because of the strong covalent bonding within the crystal. Most natural blue diamonds contain boron atoms which replace carbon atoms in the crystal matrix, and also have high thermal conductance. Specially purified synthetic diamond has the highest thermal conductivity (2000–2500 W/(m·K), five times more than copper) of any known solid at room temperature. Because diamond has such high thermal conductance it is already used in semiconductor manufacture to prevent silicon and other semiconducting materials from overheating. General Name, Symbol, Number boron, B, 5 Chemical series metalloids Group, Period, Block 13, 2, p Appearance black/brown Atomic mass 10. ... In physics, thermal conductivity, λ or k, is the intensive property of a material which relates its ability to conduct heat. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic brown Atomic mass 63. ...

Diamond's thermal conductivity is made use of by jewellers and gemologists who may employ an electronic thermal probe to separate diamonds from their imitations. These probes consist of a pair of battery-powered thermistors mounted in a fine copper tip. One thermistor functions as a heating device while the other measures the temperature of the copper tip: if the stone being tested is a diamond, it will conduct the tip's thermal energy rapidly enough to produce a measurable temperature drop. This test takes about 2–3 seconds. However, older probes will be fooled by moissanite, an imitation of diamond introduced in 1998 which has a similar thermal conductivity. A thermistor is a type of resistor used to measure temperature changes, relying on the change in its resistance with changing temperature. ... Moissanite is a trade name given to silicon carbide (chemical formula SiC) for use in the gem business. ... 1998 (MCMXCVIII) is a common year starting on Thursday of the Gregorian calendar, and was designated the International Year of the Ocean. ...

Composition and color

See also: Crystallographic defects in diamond This article addresses the possible defects of a diamond crystal. ...

Diamonds occur in a restricted variety of colors—steel gray, white, blue, yellow, orange, red, green, pink to purple, brown, and black. Colored diamonds contain crystallographic defects, including substitutional impurities and structural defects, that cause the coloration. Theoretically, pure diamonds would be transparent and colorless. Diamonds are scientifically classed into two main types and several subtypes, according to the nature of defects present and how they affect light absorption: Crystalline solids have a very regular atomic structure: that is, the local positions of atoms with respect to each other are repeated at the atomic scale. ...

Type I diamond has nitrogen (N) atoms as the main impurity, at a concentration of 0.1 percent. If the N atoms are in pairs they do not affect the diamond's color; these are Type IaA. If the N atoms are in large even-numbered aggregates they impart a yellow to brown tint (Type IaB). About 98 percent of gem diamonds are type Ia, and most of these are a mixture of IaA and IaB material: these diamonds belong to the Cape series, named after the diamond-rich region formerly known as Cape Province in South Africa, whose deposits are largely Type Ia. If the N atoms are dispersed throughout the crystal in isolated sites (not paired or grouped), they give the stone an intense yellow or occasionally brown tint (Type Ib); the rare canary diamonds belong to this type, which represents only 0.1 percent of known natural diamonds. Synthetic diamond containing nitrogen is Type Ib. Type I diamonds absorb in both the infrared and ultraviolet region, from 320 nm. They also have a characteristic fluorescence and visible absorption spectrum (see Optical properties). General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... Under the Union of South Africa and after that under the Republic of South Africa, the old Cape Colony became the Cape of Good Hope Province (though it was commonly known as the Cape Province). ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. ...

Type II diamonds have very few if any nitrogen impurities. Type IIa diamond can be colored pink, red, or brown due to structural anomalies arising through plastic deformation during crystal growth—these diamonds are rare (1.8 percent of gem diamonds), but constitute a large percentage of Australian production. Type IIb diamonds, which account for 0.1 percent of gem diamonds, are usually a steely blue or grey due to scattered boron within the crystal matrix; these diamonds are also semiconductors, unlike other diamond types (see Electrical properties). However, an overabundance of hydrogen can also impart a blue color; these are not necessarily Type IIb. Type II diamonds absorb in a different region of the infrared, and transmit in the ultraviolet below 225 nm, unlike Type I diamonds. They also have differing fluorescence characteristics, but no discernable visible absorption spectrum. A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ...

Certain diamond enhancement techniques are commonly used to artificially produce an array of colors, including blue, green, yellow, red, and black. Color enhancement techniques usually involve irradiation, including proton and deuteron bombardment via cyclotrons; neutron bombardment via the piles of nuclear reactors; and electron bombardment via Van de Graaff generators. These high-energy particles physically alter the diamond's crystal lattice, knocking carbon atoms out of place and producing color centers. The depth of color penetration depends on the technique and its duration, and in some cases the diamond may be left radioactive to some degree. This article addresses treatments designed to enhance the gemological characteristics of diamond. ... Irradiation is the process by which an item is exposed to radiation. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Deuterium (symbol 2H) is a stable isotope of hydrogen with a natural abundance of one atom in 6500 of hydrogen. ... 60-inch cyclotron, circa 1939, showing beam of accelerated ions (perhaps protons or deuterons) escaping the accelerator and ionizing the surrounding air causing a blue glow. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... Core of a nuclear reactor A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate (as opposed to a nuclear explosion, where the chain reaction occurs in a split second). ... Properties The electron is a fundamental subatomic particle which carries a negative electric charge. ... Van de Graaff generator A Van de Graaff generator is a machine which uses a moving belt to accumulate very high charges on a hollow metal globe. ... In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ...

It should be noted that some irradiated diamonds are completely natural—one famous example is the Dresden Green Diamond. In these natural stones the color is imparted by "radiation burns" in the form of small patches, usually only skin deep. Additionally, Type IIa diamonds can have their structural deformations "repaired" via a high-temperature, high-pressure (HTHP) process, removing much or all of the diamond's color. The Dresden Green diamond is a 41 carat natural green diamond, which has a historical record dating to 1722, when a London news-sheet carried an article about it in its Oct 25-27th edition. ...

In the late 18th century, diamonds were demonstrated to be made of carbon by the rather expensive experiment of igniting a diamond (by means of a burning-glass) in an oxygen atmosphere and showing that carbonic acid gas (carbon dioxide) was the product of the combustion. The fact that diamonds are combustible bears further examination because it is related to an interesting fact about diamonds. Diamonds are carbon crystals that form deep within the Earth under high temperatures and extreme pressures. At surface air pressure (one atmosphere), diamonds are not as stable as graphite, and so the decay of diamond is thermodynamically favorable (δH = −2 kJ / mol). Diamonds had previously been shown to burn during Roman times. (17th century - 18th century - 19th century - more centuries) As a means of recording the passage of time, the 18th century refers to the century that lasted from 1701 through 1800. ... A burning-glass is a large convex lens, which can focus the suns rays on a small area and so ignite materials. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Carbonic acid is a carbon-containing acid with the formula H2CO3. ... Carbon dioxide is an atmospheric gas comprised of one carbon and two oxygen atoms. ... Combustion or burning is a chemical process, an exothermic reaction between a substance (the fuel) and a gas (the oxidizer), usually O2, to release heat. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ...

So, despite De Beers' 1948 ad campaign, diamonds are definitely not forever. However, owing to a very large kinetic energy barrier, diamonds are metastable; they will not decay into graphite under normal conditions. The De Beers Group is a Johannesburg- and London-based diamond mining and trading corporation. ... Metastability is the ability of a non-equilibrium state to persist for a long period of time. ... Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time. ...

References

• O'Donoghue, Michael, and Joyner, Louise. (2003). Identification of gemstones, pp. 8–11. Butterworth-Heinemann, Great Britain. ISBN 0750655127
• Pagel-Theisen, Verena. (2001). Diamond grading ABC: The manual (9th ed.), pp. 84–85. Rubin & Son n.v.; Antwerp, Belgium. ISBN 3980043460
• Read, Peter G. (1999). Gemmology (2nd ed.). p. 52, 53, 275, 276. Butterworth-Heinemann, Great Britain. ISBN 0750644117
• Webster, Robert, and Jobbins, E. Allan (Ed.). (1998). Gemmologist's compendium, p. 21, 25, 31. St Edmundsbury Press Ltd, Bury St Edwards. ISBN 0719802911
• Webster, Robert, and Read, Peter G. (Ed.) (2000). Gems: Their sources, descriptions and identification (5th ed.), pp. 17–72. Butterworth-Heinemann, Great Britain. ISBN 0750616741
• Properties of diamond (University of Exeter)