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Diamond

2007 Schools Wikipedia Selection. Related subjects: Mineralogy


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   A scattering of round-brilliant cut diamonds shows off the many
   reflecting facets.
   Enlarge
   A scattering of round-brilliant cut diamonds shows off the many
   reflecting facets.

   Diamond is the hardest known natural material (third-hardest material
   below aggregated diamond nanorods and ultrahard fullerite), and is the
   most expensive of the two best known forms (or allotropes) of carbon,
   whose hardness and high dispersion of light make it useful for
   industrial applications and jewelry. (The other equally well known
   allotrope is graphite.) Diamonds are specifically renowned as a mineral
   with superlative physical qualities — they make excellent abrasives
   because they can be scratched only by other diamonds, Borazon,
   ultrahard fullerite, or aggregated diamond nanorods, which also means
   they hold a polish extremely well and retain luster. About 130 million
   carats (26,000 kg) are mined annually, with a total value of nearly USD
   $9 billion. About 100 tons are synthesized annually.

   The name “diamond” derives from the ancient Greek adamas (αδάμας;
   “invincible”). They have been treasured as gemstones since their use as
   religious icons in India at least 2,500 years ago—and usage in drill
   bits and engraving tools also dates to early human history. Popularity
   of diamonds has risen since the 19th century because of increased
   supply, improved cutting and polishing techniques, growth in the world
   economy, and innovative and successful advertising campaigns. They are
   commonly judged by the “four Cs”: carat, clarity, colour, and cut.
   Although synthetic diamonds are produced each year at nearly four times
   the rate of natural diamonds, the vast majority of synthetic diamonds
   produced are small imperfect diamonds suitable only for
   industrial-grade use.

   Roughly 49% of diamonds originate from central and southern Africa,
   although significant sources of the mineral have been discovered in
   Canada, India, Russia, Brazil, and Australia. They are generally mined
   from volcanic pipes, which are deep in the Earth where the high
   pressure and temperature enables the formation of the crystals. The
   mining and distribution of natural diamonds are subjects of frequent
   controversy—such as with concerns over the sale of conflict diamonds by
   African paramilitary groups. There are also allegations that the De
   Beers Group misuses its dominance in the industry to control supply and
   manipulate price via monopolistic practices, although in recent years
   the company's market share has dropped to below 60%.

Material properties

   A diamond is a transparent crystal of tetrahedrally bonded carbon
   atoms. Diamonds have been adapted for many uses because of the
   material's exceptional physical characteristics. Most notable are its
   extreme hardness of diamond, its high dispersion index, and high
   thermal conductivity.

Mechanical properties

Crystal structure

   The conventional unit cell of the diamond crystal structure.
   Enlarge
   The conventional unit cell of the diamond crystal structure.

   Diamonds typically crystallize in the face-centered cubic crystal
   system ( space group Fd\bar{3}m ) and consist of tetrahedrally bonded
   carbon atoms. The unit cell of diamond has a two atom basis at (0,0,0)
   and (1/4,1/4,1/4), which means half of the atoms are at lattice points
   and the other half are offset by (1/4,1/4,1/4), where 1 is the length
   of a side of the unit cell. Diamond's density is 3.52 g·cm^−3.

   The tetrahedral arrangement of atoms is the source of many of diamond’s
   properties. The carbon atoms in Graphite, the other major allotrope of
   carbon, display a different (nontetrahedral) connectivity and as a
   result shows dramatically different physical characteristics: graphite
   is a soft, dark gray, opaque mineral. Other elements of the carbon
   group such as silicon crystalize like diamond.

   Lonsdaleite is a polymorph of diamond (and a distinct mineral species)
   that crystallizes with hexagonal symmetry. It is rarely found in nature
   but is characteristic of synthetic diamonds. A cryptocrystalline
   variety of diamond is called carbonado. A colorless, grey to black
   diamond with a tiny radial structure is a spherulite.

Hardness

   The atomic connectivtity of the carbon atoms gives the gem its hardness
   The atomic connectivtity of the carbon atoms gives the gem its hardness

   Diamond is the hardest natural material known, scoring 10 on the
   relative Mohs scale of mineral hardness and having an absolute hardness
   value of between 90, 167, and 231 gigapascals in various tests.
   Diamond's hardness has been known since antiquity, and is the source of
   its name. However, aggregated diamond nanorods, an allotrope of carbon
   first synthesized in 2005, are now believed to be even harder than
   diamond.

   The hardest diamonds in the world are from the New England area in New
   South Wales, Australia. These diamonds are generally small, perfect to
   semiperfect octahedra, and are used to polish other diamonds. Their
   hardness is considered to be a product of the crystal growth form,
   which is single stage growth crystal. 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 (Taylor et al. 1990).

   Industrial use of diamonds has historically been associated with their
   hardness; this property makes diamond the ideal material for cutting
   and grinding tools. It is one of the most known and most useful of more
   than 3,000 known minerals. As the hardest known naturally occurring
   material, diamond can be used to polish, cut, or wear away any
   material, including other diamonds. Common industrial adaptations of
   this ability include diamond-tipped drill bits and saws, or use of
   diamond powder as an abrasive. Other specialized applications also
   exist or are being developed, including use as semiconductors: some
   blue diamonds are natural semiconductors, in contrast to most other
   diamonds, which are excellent electrical insulators. Industrial-grade
   diamonds are either unsuitable for use as gems or synthetically
   produced, which lowers their price and makes their use economically
   feasible. Industrial applications, especially as drill bits and
   engraving tools, also date to ancient times.

   The hardness of diamonds also contributes to its suitability as a
   gemstone. Because it can only be scratched by other diamonds, it
   maintains its polish extremely well, keeping its luster over long
   periods of time. 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 an engagement ring or wedding
   ring, which are often worn every day.

Toughness

   The toughness of natural diamond has been measured as 3.4 MPa\sqrt{m} ,
   which is good compared to other gemstones, but poor compared to most
   engineering materials. Toughness relates to a material's ability to
   resist breakage from forceful impact. As with any material, the
   macroscopic geometry of a diamond contributes to its resistance to
   breakage. Diamond is therefore more fragile in some orientations than
   others.

Colour

   Diamonds can occur in nearly any colour, though yellow and brown are by
   far the most common. "Black" diamonds are not truly black, but rather
   contain numerous dark inclusions that give the gems their dark
   appearance. Diamonds with a detectable hue other than yellow or brown
   are known as colored diamonds. If the colour is strong enough, a stone
   may be referred to as a fancy colored diamond by the trade. 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
   lattice. The most common impurity, nitrogen, causes a slight to intense
   yellow coloration depending upon the type and concentration of nitrogen
   present. The colour scale for colorless diamonds goes from 'D'
   (colorless) to 'Z' (dark yellow).

Thermodynamic stability

   Like other forms of carbon such as coal, diamonds will burn at
   approximately 800 degrees Celsius, providing that enough oxygen is
   available. The combustibility of diamond was shown in the late 18th
   century and previously described during Roman times. The diamond phase
   of carbon is metastable with respect to the graphitic phase under
   normal conditions; that is, graphite is thermodynamically favored over
   diamond ( ΔG = −2.99 kJ / mol). However, the rate of conversion from
   diamond to graphite is extremely slow due to the presence of a large
   kinetic barrier to this rearrangement. At room temperature, it would
   take an extremely long time (possibly more than the age of the
   Universe) for an appreciable amount of diamond to decay into graphite.

Electromagnetic properties

   Diamonds exhibit high dispersion of visible light.
   Diamonds exhibit high dispersion of visible light.

Optical properties

   Diamonds exhibit a high dispersion of visible light. This strong
   ability to split white light into its component colors is an important
   aspect of diamond's attraction as a gemstone, giving it impressive
   prismatic action that results in so-called fire in a well-cut stone.
   The luster of a diamond, its adamantine brilliance, is a consequence of
   refractive index of 2.417 (at 589.3 nm), which allows total internal
   reflection to occur easily.

   Some diamonds exhibit fluorescence of various colors (predominantly
   blue) under long wave ultraviolet radiation. Most diamonds show no
   fluorescence although colored diamonds show a wider range of
   fluorescence than the blue fluorescence normally observed in clear
   diamonds. Nearly all diamonds fluoresce bluish-white, yellow, or green
   under shorter X-ray radiation. X-ray screening is used extensively in
   mining to separate the diamond-bearing from the non-fluorescing waste
   rock.

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 conductivity. 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. The band gap of
   diamond is 5.4 - 6.4 eV.

Natural history

Formation

   Diamonds are formed by prolonged exposure of carbon bearing materials
   to high pressure and temperature. On Earth, the formation of diamonds
   is possible because there are regions deep within the Earth that are at
   a high enough pressure and temperature that the formation of diamonds
   is thermodynamically favorable. Under continental crust, diamonds form
   starting at depths of about 150 kilometers (90 miles), where pressure
   is roughly 5 gigapascals and the temperature is around 1200 degrees
   Celsius (2200 degrees Fahrenheit). Diamond formation under oceanic
   crust takes place at greater depths because of higher temperatures,
   which require higher pressure for diamond formation. Long periods of
   exposure to these high pressures and temperatures allow diamond
   crystals to grow larger.
   The slightly misshapen octahedral shape of this rough diamond crystal
   in matrix is typical of the mineral. Its lustrous faces also indicate
   that this crystal is from a primary deposit.
   Enlarge
   The slightly misshapen octahedral shape of this rough diamond crystal
   in matrix is typical of the mineral. Its lustrous faces also indicate
   that this crystal is from a primary deposit.

   Through studies of carbon isotope ratios (similar to the methodology
   used in carbon dating, except with the stable isotopes C-12 and C-13),
   it has been shown that the carbon found in diamonds comes from both
   inorganic and organic sources. Some diamonds, known as harzburgitic,
   are formed from inorganic carbon originally found deep in the Earth's
   mantle. In contrast, eclogitic diamonds contain organic carbon from
   organic detritus that has been pushed down from the surface of the
   Earth's crust through subduction (see plate tectonics) before
   transforming into diamond. These two different source carbons have
   measurably different ^13C:^12C ratios. Diamonds that have come to the
   Earth's surface are generally very old, ranging from under 1 billion to
   3.3 billion years old.

   Diamonds occur most often as euhedral or rounded octahedra and twinned
   octahedra known as macles or maccles. 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. The crystals can have rounded off and
   unexpressive edges and can be elongated. Sometimes they are found grown
   together or form double "twinned" crystals grown together at the
   surfaces of the octahedron. This is all due to the conditions in which
   they form. Diamonds (especially those with rounded crystal faces) are
   commonly found coated in nyf, an opaque gum-like skin.

   Diamonds can also form in other natural high-pressure, high-temperature
   events. Very small diamonds, known as microdiamonds or nanodiamonds,
   have been found in impact craters where meteors strike the Earth and
   create shock zones of high pressure and temperature where diamond
   formation can occur. Microdiamonds are now used as one indicator of
   ancient meteorite impact sites.

Surfacing

   Schematic diagram of a volcanic pipe
   Enlarge
   Schematic diagram of a volcanic pipe

   Diamond-bearing rock is brought close to the surface through
   deep-origin volcanic eruptions. The magma for such a volcano must
   originate at a depth where diamonds can be formed, 90 miles (150 km)
   deep or more (three times or more the depth of source magma for most
   volcanoes); this is a relatively rare occurrence. These typically small
   surface volcanic craters extend downward into formations known as
   volcanic pipes. The pipes contain material that was transported toward
   the surface by volcanic action, but was not ejected before the volcanic
   activity ceased. During eruption these pipes are open to the surface,
   resulting in open circulation; many xenoliths of surface rock and even
   wood and/or fossils are found in volcanic pipes. Diamond-bearing
   volcanic pipes are closely related to the oldest, coolest regions of
   continental crust (cratons). This is because cratons are very thick,
   and their lithospheric mantle extends to great enough depth that
   diamonds are stable. Not all pipes contain diamonds, and even fewer
   contain enough diamonds to make mining economically viable.

   The magma in volcanic pipes is usually one of two characteristic types,
   which cool into igneous rock known as either kimberlite or lamproite.
   The magma itself does not contain diamond; instead, it acts as an
   elevator that carries deep-formed rocks (xenoliths), minerals (
   xenocrysts), and fluids upward. These rocks are characteristically rich
   in magnesium-bearing olivine, pyroxene, and amphibole minerals which
   are often altered to serpentine by heat and fluids during and after
   eruption. Certain indicator minerals typically occur within
   diamondiferous kimberlites and are used as mineralogic tracers by
   prospectors, who follow the indicator trail back to the volcanic pipe
   which may contain diamonds. These minerals are rich in chromium (Cr) or
   titanium (Ti), elements which impart bright colors to the minerals. The
   most common indicator minerals are chromian garnets (usually bright red
   Cr- pyrope, and occasionally green ugrandite-series garnets), eclogitic
   garnets, orange Ti-pyrope, red high-Cr spinels, dark chromite, bright
   green Cr- diopside, glassy green olivine, black picroilmenite, and
   magnetite. Kimberlite deposits are known as blue ground for the deeper
   serpentinized part of the deposits, or as yellow ground for the near
   surface smectite clay and carbonate weathered and oxidized portion.

   Once diamonds have been transported to the surface by magma in a
   volcanic pipe, they may erode out and be distributed over a large area.
   A volcanic pipe containing diamonds is known as a primary source of
   diamonds. Secondary sources of diamonds include all areas where a
   significant number of diamonds, eroded out of their kimberlite or
   lamproite matrix, accumulate because of water or wind action. These
   include alluvial deposits and deposits along existing and ancient
   shorelines, where loose diamonds tend to accumulate because of their
   approximate size and density. Diamonds have also rarely been found in
   deposits left behind by glaciers (notably in Wisconsin and Indiana);
   however, in contrast to alluvial deposits, glacial deposits are not
   known to be of significant concentration and are therefore not viable
   commercial sources of diamond.

   Diamonds can also be brought to the surface through certain processes
   which may occur when two continental plates collide and deeply formed
   rock is thrust to the surface, although this phenomenon is less
   understood and currently assumed to be uncommon.

Gemological characteristics

   The use of diamonds as gemstones of decorative value is the most
   familiar use to most people today, and is also the earliest use, with
   decorative use of diamonds stretching back into antiquity. The
   dispersion of white light into a rainbow of colors, known in the trade
   as fire, is the other primary characteristic of gem diamonds, and has
   been highly prized throughout history. Over time, especially since
   around 1900, experts in the field of gemology have developed methods of
   characterizing diamonds and other gemstones based on the
   characteristics most important to their value as a gem. Four
   characteristics, known informally as the four Cs, are now commonly used
   as the basic descriptors of diamonds: these are carat, clarity, colour,
   and cut.

   Most gem diamonds are traded on the wholesale market based on single
   values for each of the four Cs; for example knowing that a diamond is
   rated as 1.5 carats, VS2 clarity, F colour, excellent cut, is enough to
   reasonably establish an expected price range. More detailed information
   from within each characteristic can then be used to determine actual
   market value for individual stones. Consumers who purchase individual
   diamonds are often advised to use the four Cs to pick the diamond that
   is "right" for them; to these is sometimes added the "fifth C" of
   credentials.

   Other characteristics not described by the four Cs can and do influence
   the value or appearance of a gem diamond. These characteristics include
   physical characteristics such as the presence of fluorescence, as well
   as data on a diamond's history including its source and which
   gemological institute performed evaluation services on the diamond.
   Cleanliness also dramatically affects a diamond's beauty.

   There are three major non profit gemological associations which
   "certify" diamonds: that is, define the four Cs of a diamond. While
   carat weight and cut angles are mathematically defined, the clarity and
   colour are judged by the trained human eye and are therefore open to
   slight variance in interpretation.
     * Gemological Institute of America (GIA) was one the first laboratory
       to issue modern diamond reports, and is held in high regard amongst
       gemologists for its consistent, conservative grading.
     * Diamond High Council (HRD) Official certification laboratory of the
       Belgian diamond industry. ISO9002 certified. Very popular in Europe
       where it is recognized as a legal document.
     * American Gemological Society (AGS) is not as widely recognized nor
       as old as the GIA, but garners a high reputation. Uses non standard
       naming of colour,clarity and cut i.e. numbers rather than letters.

Carat

   The carat weight measures the mass of a diamond. One carat is defined
   as a fifth of a gram, or exactly 200 milligrams (about 0.007 ounce).
   The point unit—equal to one one-hundredth of a carat (0.01 carat, or 2
   mg)—is commonly used for diamonds of less than one carat. All else
   being equal, the value of a diamond increases exponentially in relation
   to carat weight, since larger diamonds are both rarer and more
   desirable for use as gemstones. A review of comparable diamonds
   available for purchase in September 2005 demonstrates this effect
   (approximate prices for round cut, G colour, VS2 diamonds with "1A" cut
   grade, as listed on http://www.pricescope.com):
        Carat size       Cost per carat (US$) Total cost (US$)
   0.5 carat (50 points)                3,000            1,500
   1.0 carat                            6,500            6,500
   1.5 carats                           8,500           12,750
   2.0 carats                          13,000           26,000
   3.0 carats                          17,000           51,000
   5.0 carats                          23,000          115,000

   The price per carat does not increase smoothly with increasing size.
   Instead, there are sharp jumps around milestone carat weights, as
   demand is much higher for diamonds weighing just more than a milestone
   than for those weighing just less. As an example, a 0.95 carat diamond
   may have a significantly lower price per carat than a comparable 1.05
   carat diamond, because of differences in demand.

   A weekly diamond price list, the Rapaport Diamond Report , is published
   by Martin Rapaport, CEO of Rapaport Group of New York, for different
   diamond cuts, clarity and weights. It is currently considered the
   de-facto retail price baseline. Jewelers often trade diamonds at
   negotiated discounts off the Rapaport price (e.g., "R -3%").

   In the wholesale trade of gem diamonds, carat is often used in
   denominating lots of diamonds for sale. For example, a buyer may place
   an order for 100 carats of 0.5 carat, D–F, VS2-SI1, excellent cut
   diamonds, indicating he wishes to purchase 200 diamonds (100 carats
   total mass) of those approximate characteristics. Because of this,
   diamond prices (particularly among wholesalers and other industry
   professionals) are often quoted per carat, rather than per stone.

   Total carat weight (t.c.w.) is a phrase used to describe the total mass
   of diamonds or other gemstone in a piece of jewelry, when more than one
   gemstone is used. Diamond solitaire earrings, for example, are usually
   quoted in t.c.w. when placed for sale, indicating the mass of the
   diamonds in both earrings and not each individual diamond. T.c.w. is
   also widely used for diamond necklaces, bracelets and other similar
   jewelry pieces.

Clarity

   Clarity is a measure of internal defects of a diamond called
   inclusions. Inclusions may be crystals of a foreign material or another
   diamond crystal, or structural imperfections such as tiny cracks that
   can appear whitish or cloudy. The number, size, colour, relative
   location, orientation, and visibility of inclusions can all affect the
   relative clarity of a diamond. The Gemological Institute of America
   (GIA) and others have developed systems to grade clarity, which are
   generally based on those inclusions which are visible to a trained
   professional when a diamond is viewed from above, under 10x
   magnification.

   Diamonds become increasingly rare when considering higher clarity
   gradings. Only about 20 percent of all diamonds mined have a clarity
   rating high enough for the diamond to be considered appropriate for use
   as a gemstone; the other 80 percent are relegated to industrial use. Of
   that top 20 percent, a significant portion contains a visible inclusion
   or inclusions. Those that do not have a visible inclusion are known as
   "eye-clean" and are preferred by most buyers, although visible
   inclusions can sometimes be hidden under the setting in a piece of
   jewelry.

   Most inclusions present in gem-quality diamonds do not affect the
   diamonds' performance or structural integrity. However, large clouds
   can affect a diamond's ability to transmit and scatter light. Large
   cracks close to or breaking the surface may reduce a diamond's
   resistance to fracture.

   Diamonds are graded by the major societies on a scale ranging from
   flawless to imperfect.

Colour

   Jewelers sometimes set diamonds in groups of similar colors.
   Enlarge
   Jewelers sometimes set diamonds in groups of similar colors.
   The Hope Diamond. Its deep blue coloration is caused by trace amounts
   of boron in the diamond.
   Enlarge
   The Hope Diamond. Its deep blue coloration is caused by trace amounts
   of boron in the diamond.

   A chemically pure and structurally perfect diamond is perfectly
   transparent with no hue, or colour. However, in reality almost no
   gem-sized natural diamonds are absolutely perfect. The colour of a
   diamond may be affected by chemical impurities and/or structural
   defects in the crystal lattice. Depending on the hue and intensity of a
   diamond's coloration, a diamond's colour can either detract from or
   enhance its value. For example, most white diamonds are discounted in
   price as more yellow hue is detectable, while intense pink or blue
   diamonds (such as the Hope Diamond) can be dramatically more valuable.

   Most diamonds used as gemstones are basically transparent with little
   tint, or white diamonds. The most common impurity, nitrogen, replaces a
   small proportion of carbon atoms in a diamond's structure and causes a
   yellowish to brownish tint. This effect is present in almost all white
   diamonds; in only the rarest diamonds is the coloration due to this
   effect undetectable. The GIA has developed a rating system for color in
   white diamonds, from "D" to "Z" (with D being "colorless" and Z having
   a bright yellow coloration), which has been widely adopted in the
   industry and is universally recognized, superseding several older
   systems once used in different countries. The system uses a benchmark
   set of either natural diamonds of known colour grade, or
   precision-crafted cubic zirconia; test lighting conditions are also
   standardized and carefully controlled. Diamonds with higher color
   grades are rarer, in higher demand, and therefore more expensive, than
   lower color grades. Oddly enough, diamonds graded Z are also rare, and
   the bright yellow colour is also highly valued. Diamonds graded D-F are
   considered "colorless", G-J are considered "near-colorless", K-M are
   "slightly colored". N-Y usually appear light yellow or brown.

   In contrast to yellow or brown hues, diamonds of other colors are much
   rarer and more valuable. While even a pale pink or blue hue may
   increase the value of a diamond, more intense coloration is usually
   considered more desirable and commands the highest prices. A variety of
   impurities and structural imperfections cause different colors in
   diamonds, including yellow, pink, blue, red, green, brown, and other
   hues. Diamonds with unusual or intense coloration are sometimes labeled
   "fancy" by the diamond industry. Intense yellow coloration is
   considered one of the fancy colors, and is separate from the colour
   grades of white diamonds. Gemologists have developed rating systems for
   fancy colored diamonds, but they are not in common use because of the
   relative rarity of colored diamonds.

Cut

   Diamond cutting is the art and science of creating a gem-quality
   diamond out of mined rough. The cut of a diamond describes the manner
   in which a diamond has been shaped and polished from its beginning form
   as a rough stone to its final gem proportions. The cut of a diamond
   describes the quality of workmanship and the angles to which a diamond
   is cut. Often diamond cut is confused with "shape."

   There are mathematical guidelines for the angles and length ratios at
   which the diamond is supposed to be cut in order to reflect the maximum
   amount of light. Round brilliant diamonds, the most common, are guided
   by these specific guidelines, though fancy cut stones are not able to
   be as accurately guided by mathematical specifics.

   The techniques for cutting diamonds have been developed over hundreds
   of years, with perhaps the greatest achievements made in 1919 by
   mathematician and gem enthusiast Marcel Tolkowsky. He developed the
   round brilliant cut by calculating the ideal shape to return and
   scatter light when a diamond is viewed from above. The modern round
   brilliant has 57 facets (polished faces), counting 33 on the crown (the
   top half), and 24 on the pavilion (the lower half). The girdle is the
   thin middle part. The function of the crown is to diffuse light into
   various colours and the pavilion's function to reflect light back
   through the top of the diamond.

   Tolkowsky defines the ideal dimensions to have:
     * Table percentage (table diameter divided by overall diameter) = 53%
     * Depth percentage (Overall depth divided by the overall diameter) =
       59.3%
     * Pavilion Angle (Angle between the girdle and the pavilion) = 40.75°
     * Crown Angle (Angle between the girdle and the crown) = 34.5°
     * Pavilion Depth (Depth of pavilion divided by overall diameter) =
       43.1%
     * Crown Depth (Depth of crown divided by crown diameter) = 16.2%

   The culet is the tiny point or facet at the bottom of the diamond. This
   should be a negligible diameter, otherwise light leaks out of the
   bottom. Tolkowsky's ideal dimensions did not include a girdle. However,
   a thin girdle is required in reality in order to prevent the diamond
   from easily chipping in the setting. A normal girdle should be about
   1%–2% of the overall diameter.

   The further the diamond's characteristics are from Tolkowsky's ideal,
   the less light will be reflected. However, there is a small range in
   which the diamond can be considered "ideal." Today, because of the
   relative importance of carat weight in society, many diamonds are often
   intentionally cut poorly to increase carat weight. There is a financial
   premium for a diamond that weighs the magical 1.0 carat, so often the
   girdle is made thicker or the depth is increased. Neither of these
   tactics make the diamond appear any bigger, and they greatly reduce the
   sparkle of the diamond. So a poorly cut 1.0 carat diamond may have the
   same diameter and appear as large as a 0.85 carat diamond. The depth
   percentage is the overall quickest indication of the quality of the cut
   of a round brilliant. "Ideal" round brilliant diamonds should not have
   a depth percentage greater than 62.5%. Another quick indication is the
   overall diameter. Typically a round brilliant 1.0 carat diamond should
   have a diameter of about 6.5 mm. Mathematically, the diameter in
   millimeters of a round brilliant should approximately equal 6.5 times
   the cube root of carat weight, or 11.1 times the cube root of gram
   weight, or 1.4 times the cube root of point weight.

Shape

   Diamonds do not show all of their beauty as rough stones; instead, they
   must be cut and polished to exhibit the characteristic fire and
   brilliance that diamond gemstones are known for. Diamonds are cut into
   a variety of shapes that are generally designed to accentuate these
   features.

   Diamonds which are not cut to the specifications of Tolkowsky's round
   brilliant shape (or subsequent variations) are known as "fancy cuts."
   Popular fancy cuts include the baguette (from the French, meaning rod
   or loaf of bread), marquise, princess (square outline), heart,
   briolette (a form of the rose cut), and pear cuts. Newer cuts that have
   been introduced into the jewelry industry are the "cushion"
   "radiant"(similar to princess cuts, but with rounded edges instead of
   square edges) and "ascher" cuts. Many fancy colored diamonds are now
   being cut according to these new styles. Generally speaking, these
   "fancy cuts" are not held to the same strict standards as
   Tolkowsky-derived round brilliants and there are less specific
   mathematical guidelines of angles which determine a well-cut stone.
   Cuts are influenced heavily by fashion: the baguette cut—which
   accentuates a diamond's luster and downplays its fire—was all the rage
   during the Art Deco period, whereas the princess cut—which accentuates
   a diamond's fire rather than its luster—is currently gaining
   popularity. The princess cut is also popular amongst diamond cutters:
   of all the cuts, it wastes the least of the original crystal. The past
   decades have seen the development of new diamond cuts, often based on a
   modification of an existing cut. Some of these include extra facets.
   These newly developed cuts are viewed by many as more of an attempt at
   brand differentiation by diamond sellers, than actual improvements to
   the state of the art.

Quality

   The quality of a diamond's cut is widely considered the most important
   of the four Cs in determining the beauty of a diamond; indeed, it is
   commonly acknowledged that a well-cut diamond can appear to be of
   greater carat weight, and have clarity and colour appear to be of
   better grade than they actually are. The skill with which a diamond is
   cut determines its ability to reflect and refract light.

   In addition to carrying the most importance to a diamond's quality as a
   gemstone, the cut is also the most difficult to quantitatively judge. A
   number of factors, including proportion, symmetry, and the relative
   angles of various facets, are determined by the quality of the cut and
   can affect the performance of a diamond. A poorly cut diamond with
   facets cut only a few degrees out of alignment can result in a poorly
   performing stone. For a round brilliant cut, there is a balance between
   "brilliance" and "fire." When a diamond is cut for too much "fire," it
   looks like a cubic zirconia, which gives off much more "fire" than real
   diamond. A well-executed round brilliant cut should reflect light
   upwards and make the diamond appear white when viewed from the top. An
   inferior cut will produce a stone that appears dark at the centre and
   in some extreme cases the ring settings may show through the top of the
   diamond as shadows.

   Several different theories on the "ideal" proportions of a diamond have
   been and continue to be advocated by professional gemologists.
   Recently, there has been a shift away from grading cut by the use of
   various angles and proportions toward measuring the performance of a
   cut stone. A number of specially modified viewers and machines have
   been developed toward this end. They included the FireScope, a.k.a.
   SymmetriScope or IdealScope (tests for light leakage, light return and
   proportions), Hearts and Arrows Viewer (test for " hearts and arrows"
   characteristic pattern observable on stones exhibiting high symmetry),
   GemEx BrillianceScope (tests for direct light performance results of a
   diamond), Isee2 Beauty Evaluator (tests for diffused light performance
   results for round or octagonal diamonds), and ASET (test for AGS cut
   grade). These viewers and machines often help consumers determine the
   light performance results of the diamond in addition to the traditional
   4 C's. Along with this shift there are a few companies that provide
   results on these viewers and machines in addition to the original 4c's.
   The GIA has also developed criteria for grading the cut of round
   brilliant stones.

The cutting process

   An uncut diamond does not show its prized optical properties.
   Enlarge
   An uncut diamond does not show its prized optical properties.

   The process of shaping a rough diamond into a polished gemstone is both
   an art and a science. The choice of cut is often decided by the
   original shape of the rough stone, location of the inclusions and flaws
   to be eliminated, the preservation of the weight, popularity of certain
   shapes amongst consumers and many other considerations. The round
   brilliant cut is preferred when the crystal is an octahedron, as often
   two stones may be cut from one such crystal. Oddly shaped crystals such
   as macles are more likely to be cut in a fancy cut—that is, a cut other
   than the round brilliant—which the particular crystal shape lends
   itself to.

   Even with modern techniques, the cutting and polishing of a diamond
   crystal always results in a dramatic loss of weight; rarely is it less
   than 50%. Sometimes the cutters compromise and accept lesser
   proportions and symmetry in order to avoid inclusions or to preserve
   the carat rating. Since the per carat price of diamond shifts around
   key milestones (such as 1.00 carat), many one-carat diamonds are the
   result of compromising "Cut" for "Carat." Some jewelry experts advise
   consumers to buy a 0.99 carat diamond for its better price or buy a
   1.10 carat diamond for its better cut, avoiding a 1.00 carat diamond
   which is more likely to be a poorly cut stone.

Light Performance

   Light performance deals with how much light, what kind of light and the
   origin of light being emitted or reflected by a diamond when subject to
   a light source.

   Performance has often been associated with cars, stereos, boats,
   watches, and computers, but rarely been it ever been used to describe a
   diamond. The degree a diamond is able to radiate light determines its
   beauty, desirability, and value. Thus it is important that its light
   performance be quantified and compared with other diamonds. Where
   proportions are used to forecast results light performance goes after
   the bottom line, the actual light output from a diamond. For the end
   users the information on the light performance of a diamond has the
   greatest relevance because they will know how much light they are
   getting for their money. This is analogous to knowing what the wattage
   of a light bulb is before one makes a purchase. Knowing how a product
   performs relative to others in the market is critical for consumers
   whether they are purchasing a cell phone, CD player or a truck.

Cleaning

   Although it is not one of the four Cs, cleanliness affects a diamond's
   beauty as much as any of the four Cs. A clean diamond is more brilliant
   and fiery than the same diamond when it is "dirty." Dirt or grease on
   the top of a diamond reduces its luster. Water, dirt, or grease on the
   bottom of a diamond interferes with the diamond's brilliance and fire.
   Even a thin film absorbs some light that could have been reflected to
   the person looking at the diamond. Colored dye or smudges can affect
   the perceived color of a diamond. Historically, some jewelers' stones
   were misgraded because of smudges on the girdle, or dye on the culet.
   Current practice is to thoroughly clean a diamond before grading its
   colour.

   Maintaining a clean diamond can sometimes be difficult, as jewelry
   settings can obstruct cleaning efforts, and oils, grease, and other
   hydrophobic materials adhere well to a diamond's surface. Some jewelers
   provide their customers with ammonia-based cleaning kits; ultrasonic
   cleaners are also popular.

   Cleanliness does not affect the diamond's market value, as any
   competent jeweler will clean the diamond before offering it for sale.
   However, cleanliness might reflect a diamond's sentimental value: some
   jewelers have noted a correlation between ring cleanliness and marriage
   quality .

History

   Diamonds are thought to have been first recognized and mined in India,
   where significant alluvial deposits of the stone could then be found.
   The earliest written reference can be found in the Buddhist text, the
   Anguttara Nikaya another sanskrit text, the Arthashastra, which was
   completed around 296 BCE and describes diamond's hardness, luster, and
   dispersion. Diamonds quickly became associated with divinity, being
   used to decorate religious icons, and were believed to bring good
   fortune to those who carried them. Ownership was restricted among
   various castes by colour, with only kings being allowed to own all
   colors of diamond.

   In February 2005, a joint Chinese-U.S. team of archaeologists reported
   the discovery of four corundum-rich stone ceremonial burial axes
   originating from China's Liangzhu and Sanxingcun cultures (4000
   BCE–2500 BCE) which, because of the axes' specular surfaces, the
   scientists believe were polished using diamond powder . Although there
   are diamond deposits now known to exist close to the burial sites, no
   direct evidence of coeval diamond mining has been found: the
   researchers came to this conclusion by polishing corundum using various
   lapidary abrasives and modern techniques then comparing the results
   using an atomic force microscope. At that scale, the surface of the
   modern diamond-polished corundum closely resembled that of the axes;
   however, the polishes of the latter were superior.

   Diamonds were traded to both the east and west of India and were
   recognized by various cultures for their gemological or industrial
   uses. In his work Naturalis Historia, the Roman writer Pliny the Elder
   noted diamond's ornamental uses, as well as its usefulness to engravers
   because of its hardness. In China, diamonds seem to have been used
   primarily as diamond tools for engraving jade and drilling holes in
   beads. Archaeological evidence from Yemen suggests that diamonds were
   used as drill tips as early as the 4th century BCE. In Europe, however,
   diamonds disappeared for almost 1,000 years following the rise of
   Christianity because of two effects: early Christians rejected diamonds
   because of their earlier use in amulets, and Arabic traders restricted
   the flow of trade between Europe and India.
   Diagram of old diamond cuts showing the evolution from the most
   primitive (point cut) to the most advanced pre-Tolkowsky cut (old
   European).
   Enlarge
   Diagram of old diamond cuts showing the evolution from the most
   primitive (point cut) to the most advanced pre- Tolkowsky cut (old
   European).

   Until the late Middle Ages, diamonds were most prized in their natural
   octahedral state, perhaps with the crystal surfaces polished to
   increase luster and remove foreign material. Around 1300, the flow of
   diamonds into Europe increased via Venice's trade network, with most
   flowing through the low country ports of Bruges, Antwerp, and
   Amsterdam. During this time, the taboo against cutting diamonds into
   gem shapes, which was established over 1,000 years earlier in the
   traditions of India, ended allowing the development of diamond cutting
   technology to begin in earnest. By 1375, a guild of diamond polishers
   had been established at Nuremberg. Over the following centuries,
   various diamond cuts were introduced which increasingly demonstrated
   the fire and brilliance that makes diamonds treasured today: the table
   cut, the briolette (around 1476), the rose cut (mid-16th century), and
   by the mid-17th century, the Mazarin, the first brilliant cut diamond
   design. In 1919, Marcel Tolkowsky developed an ideal round brilliant
   cut design that has set the standard for comparison of modern gems;
   however, diamond cuts have continued to be refined.

   The rise in popularity of diamonds as gems seems to have paralleled
   increasing availability through European history. In the 13th century,
   King Louis IX of France established a law that only the king could own
   diamonds. However, within a century diamonds were popular gems among
   the moneyed aristocratic and merchant classes, and by at latest 1477
   had begun to be used in wedding rings. Popularity continued to rise as
   new cuts were developed that enhanced the diamond's aesthetic appeal,
   and has largely continued unabated to this day; diamonds have proven
   popular with all classes in society as their cost has become within
   reach. A number of large diamonds have become historically significant
   objects, as their inclusion in various sets of crown jewels and the
   purchase, sale, and sometimes theft of notable diamonds, have sometimes
   become politicized.

Record-holding Diamonds

   The Cullinan Diamond, part of the British crown jewels, was the largest
   gem-quality rough diamond ever found (1905), at 3,106.75 carats. One of
   the diamonds cut from it, Cullinan I or the Great Star of Africa, was
   formerly the largest gem-quality cut diamond at 530.2 carats, but now
   that title has been taken by the Golden Jubilee (1985), a 545.67 carat,
   yellow-brown diamond. The largest flawless and colorless (grade D)
   diamond is the Centenary Diamond which weighs 273.85 carats. The
   Millennium Star is the second largest (1990) at 203.04 carats.

The diamond industry

   A round brilliant cut diamond set in a ring.
   A round brilliant cut diamond set in a ring.

   The diamond industry can be broadly separated into two basically
   distinct categories: one dealing with gem-grade diamonds and another
   for industrial-grade diamonds. While a large trade in both types of
   diamonds exists, the two markets act in dramatically different ways.

Gem diamond industry

   A large trade in gem-grade diamonds exists. Unlike precious metals such
   as gold or platinum, gem diamonds do not trade as a commodity: there is
   a substantial mark-up in the sale of diamonds, and there is not a very
   active market for resale of diamonds. One hallmark of the trade in
   gem-quality diamonds is its remarkable concentration: wholesale trade
   and diamond cutting is limited to a few locations (most importantly New
   York, Antwerp, London, Tel Aviv, Amsterdam and Surat), and a single
   company— De Beers—controls a significant proportion of the trade in
   diamonds. They are based in Johannesburg, South Africa and London,
   England.

   The production and distribution of diamonds is largely consolidated in
   the hands of a few key players, and concentrated in traditional diamond
   trading centers (the most important being Antwerp). The De Beers
   company, as the world's largest diamond miner holds a clearly dominant
   position in the industry, and has done so since soon after its founding
   in 1888 by the British imperialist Cecil Rhodes. De Beers owns or
   controls a significant portion of the world's rough diamond production
   facilities (mines) and distribution channels for gem-quality diamonds.
   The company and its subsidiaries own mines that produce some 40 percent
   of annual world diamond production. At one time it was thought over 80
   percent of the world's rough diamonds passed through the Diamond
   Trading Company (DTC, a subsidiary of De Beers) in London, but
   presently the figure is estimated at less than 50 percent. De Beers
   used its monopoly position to establish strict price controls, and
   market diamonds directly to consumers in world markets.

   The De Beers diamond advertising campaign is acknowledged as one of the
   most successful and innovative ones in history. N.W. Ayer & Son, the
   advertising firm retained by De Beers in the mid-20th century,
   succeeded in reviving the American diamond market and opened up new
   markets, even in countries where no diamond tradition had existed
   before. N.W. Ayer's multifaceted marketing campaign included product
   placement, advertising the diamond itself rather than the De Beers
   brand, and building associations with celebrities and royalty. This
   coordinated campaign has lasted decades and continues today; it is
   perhaps best captured by the now-familiar slogan "a diamond is
   forever". The De Beers account is now handled by the firm JWT, formerly
   known as J. Walter Thompson.

   Further down the supply chain, members of The World Federation on
   Diamond Bourses (WFDB) act as a medium for wholesale diamond exchange,
   trading both polished and rough diamonds. The WFDB consists of
   independent diamond bourses in major cutting centres such as Israel,
   Antwerp, Johannesburg and other cities across the USA, Europe and Asia.

   In 2000, the WFDB and The International Diamond Manufacturers
   Association established the World Diamond Council to prevent the
   trading of diamonds used to fund war and inhumane acts.

   WFDB's additional activities also include sponsoring the World Diamond
   Congress every two years, as well as the establishment of the
   International Diamond Council (IDC) to oversee diamond grading.
   However, due to the dominance of such labs as The Gemmological
   Institute of America (GIA), compliance with IDC rules is mostly
   confined to smaller laboratories.

Industrial diamond industry

   The market for industrial-grade diamonds operates much differently from
   its gem-grade counterpart. Industrial diamonds are valued mostly for
   their hardness and heat conductivity, making many of the gemological
   characteristics of diamond, including clarity and colour, mostly
   irrelevant. This helps explain why 80% of mined diamonds (equal to
   about 100 million carats or 20,000 kg annually), unsuitable for use as
   gemstones and known as bort, are destined for industrial use. In
   addition to mined diamonds, synthetic diamonds found industrial
   applications almost immediately after their invention in the 1950s;
   another 400 million carats (80,000 kg) of synthetic diamonds are
   produced annually for industrial use—nearly four times the mass of
   natural diamonds mined over the same period.

   The dominant industrial use of diamond is in cutting, drilling,
   grinding, and polishing. Most uses of diamonds in these technologies do
   not require large diamonds; in fact, most diamonds that are gem-quality
   except for their small size, can find an industrial use. Diamonds are
   embedded in drill tips or saw blades, or ground into a powder for use
   in grinding and polishing applications. Specialized applications
   include use in laboratories as containment for high pressure
   experiments (see diamond anvil), high-performance bearings, and limited
   use in specialized windows.

   With the continuing advances being made in the production of synthetic
   diamond, future applications are beginning to become feasible.
   Garnering much excitement is the possible use of diamond as a
   semiconductor suitable to build microchips from, or the use of diamond
   as a heat sink in electronics. Significant research efforts in Japan,
   Europe, and the United States are under way to capitalize on the
   potential offered by diamond's unique material properties, combined
   with increased quality and quantity of supply starting to become
   available from synthetic diamond manufacturers.

Diamond supply chain

   The diamond supply chain is controlled by a limited number of powerful
   businesses, and is also highly concentrated in a small number of
   locations around the world. In fact, the amount of power which De Beers
   has consolidated historically prevented it from direct trade with the
   United States, as its trade practices led to an indictment for
   violating antitrust regulations (the case was settled in 2004). The
   concentration of power only loosens at the retail level, where diamonds
   are sold by a limited number of distributors, known as sightholders, to
   jewelers around the world.
   Alluvial mining by traditional methods continues, as seen here in
   Sierra Leone.
   Enlarge
   Alluvial mining by traditional methods continues, as seen here in
   Sierra Leone.

Mining

   Only a very small fraction of the diamond ore consists of actual
   diamonds. The ore is crushed, during which care has to be taken in
   order to prevent larger diamonds from being destroyed in this process
   and subsequently the particles are sorted by density. Nowadays, the
   diamonds are located in the diamond-rich density fraction with the help
   of X-ray fluorescence, after which the final sorting steps are done by
   hand. Before the use of X-rays became commonplace, the separation was
   done with grease belts; diamonds have a stronger tendency to stick to
   grease than the other minerals in the ore.

Distribution

   The Diamond Trading Company, or DTC, is a subsidiary of De Beers and
   markets rough diamonds produced both by De Beers mines and other mines
   from which it purchases rough diamond production. DTC performs
   sophisticated sorting of rough diamonds into over 16,000 categories,
   and then sells bulk lots of rough diamonds to a limited number of
   sightholders a few times a year.

   Once purchased by sightholders, diamonds are cut and polished in
   preparation for sale as gemstones. The cutting and polishing of rough
   diamonds is a specialized skill that is concentrated in a limited
   number of locations worldwide. Traditional diamond cutting centers are
   Antwerp, Amsterdam, Johannesburg, New York, and Tel Aviv. Recently,
   diamond cutting centers have been established in China, India, and
   Thailand. Cutting centers with lower costs of labor, notably Surat in
   Gujarat, India, handle a larger number of smaller carat diamonds, while
   smaller quantities of larger or more valuable diamonds are more likely
   to be handled in Europe or North America. Demonstrating this, India
   produces 90% of all cut and polished diamonds by number, but only 55%
   by value. The recent expansion of this industry in India, employing low
   cost labor, has allowed smaller diamonds to be prepared as gems than
   was previously economically feasible.

   Diamonds which have been prepared as gemstones are sold on diamond
   exchanges called bourses. There are 24 registered diamond bourses. This
   is the final tightly controlled step in the diamond supply chain;
   wholesalers and even retailers are able to buy relatively small lots of
   diamonds at the bourses, after which they are prepared for final sale
   to the consumer. Diamonds can be sold already set in jewelry, or as is
   increasingly popular, sold unset ("loose"). According to the Rio Tinto
   Group, in 2002 the diamonds produced and released to the market were
   valued at US$9 billion as rough diamonds, US$14 billion after being cut
   and polished, US$28 billion in wholesale diamond jewelry, and retail
   sales of US$57 billion.

Synthetics, Simulants, and enhancements

   It is important to distinguish that a synthetic diamond is a true
   diamond created by a technological process, whereas a diamond simulant
   is defined as a non-diamond material that is used to simulate the
   appearance of a true diamond.

   The gemological and industrial uses of diamond have created a large
   demand for raw stones. A portion of this demand is now being met by
   synthetic diamonds, artificially-made diamonds which have similar
   properties to natural diamonds. This process has historically produced
   industrial-grade diamonds, but synthetic diamond producers have
   recently begun to produce diamonds with high enough quality to
   penetrate the gem diamond market. Diamonds have been manufactured
   synthetically for over fifty years.

   A diamond's gem quality, which is not as dependent on material
   properties as industrial applications, has invited both imitation and
   the invention of procedures to enhance the gemological properties of
   natural diamonds. Materials which have similar gemological
   characteristics to diamond but are not mined or synthetic diamond are
   known as diamond simulants. The most familiar diamond simulant to most
   consumers is cubic zirconia (commonly abbreviated as CZ); recently
   moissanite has also gained cachet as a popular diamond simulant. Both
   CZ and moissanite are synthetically produced for use as a diamond
   simulant. Diamond enhancements are specific treatments, performed on
   natural diamonds (usually those already cut and polished into a gem),
   which are designed to better the gemological characteristics of the
   stone in one or more ways. These include laser drilling to remove
   inclusions, application of sealants to fill cracks, treatments to
   improve a white diamond's color grade, and treatments to give fancy
   colour to a white diamond.

   Currently, trained gemologists with appropriate equipment are able to
   distinguish natural diamonds from all synthetic and simulant diamonds,
   and identify all enhanced natural diamonds. The established natural
   diamond industry has a vested interest in maintaining the distinction
   between natural diamonds and other diamonds, and has made significant
   investments toward that end. However, as manufacturing technology
   improves, synthetic diamonds may become indistinguishable from natural
   diamonds, and new techniques for creating and treating simulants (such
   as coating them with a very thin diamond-like layer of carbon) are
   making it increasingly difficult to distinguish simulants from real
   diamonds.

Symbolism

   Mary of Burgundy is the first known recipient of a diamond engagement
   ring, in 1477.
   Enlarge
   Mary of Burgundy is the first known recipient of a diamond engagement
   ring, in 1477.

   Because of their extraordinary physical properties, diamonds have been
   used symbolically since near the time of their first discovery. Perhaps
   the earliest symbolic use of diamonds was as the eyes of Hindu
   devotional statues. In Hinduism Indra uses Vajrayudham or the
   thunderbolt as his primary weapon. Vajra is the word for diamond and
   ayudham means weapon in Sanskrit. The diamonds themselves were thought
   to be endowments from the gods and were therefore cherished. The point
   at which diamonds began to be associated with divinity is not known,
   but early texts indicate that it was recognized in India since at least
   400 BCE. It is said the Greeks believed diamonds were tears of the
   gods; the Romans believed they were splinters of fallen stars. Many
   long dead cultures have sought to explain diamond's superlative
   properties through divine or mystical affiliations.

   In Tibetan Buddhism, also known as Vajrayana (Diamond Vehicle),
   diamonds are an important symbol, and the Diamond Sutra is one of the
   most popular texts.

   In Western culture, diamonds are the traditional emblem of fearlessness
   and virtue, but have also often associated with power, wealth, crime
   and misfortune. Today, diamonds are used to symbolize eternity and
   love, being often seen adorning engagement rings and sometimes wedding
   rings as well. The popularity of this modern tradition can be traced
   directly to the marketing campaigns of De Beers, starting in 1938.
   Prior to the De Beers marketing campaign, engagement rings had no one
   particular stone associated with them. The first diamond engagement
   ring can be traced to the marriage of Maximilian I (then Archduke of
   Austria) to Mary of Burgundy in 1477. Other early examples of betrothal
   jewels incorporating diamonds include the Bridal Crown of Blanche (ca.
   1370–80) and the Heftlein brooch of Vienna (ca. 1430–40), a pictorial
   piece depicting a wedding couple. Inaccessibility of diamonds to the
   vast majority of the population limited the popularity of diamonds as
   betrothal jewels during this period.

   The LifeGem company further taps modern symbolism by purporting to
   synthetically convert the carbonized remains of people or pets into
   "memorial diamonds." However, many people feel very uncomfortable at
   the thought of wearing the carbonized remains of people as jewelry.

   The diamond is the birthstone for people born in the month of April,
   and is also used as the symbol of a sixty-year anniversary, such as a
   Diamond Jubilee (see hierarchy of precious substances).

   Diamonds are a common focus of fiction. Notable pieces of fiction
   include Ian Fleming's Diamonds Are Forever (1956), Arthur C. Clarke's
   2061: Odyssey Three (1988), F. Scott Fitzgerald's "The Diamond as Big
   As the Ritz" (1922), and Neal Stephenson's The Diamond Age (1995). In
   addition, diamonds are the subject of various myths and legends.

Symbolism in the Occult

   Historically, and in occultist myths, it has been claimed that diamonds
   possess several supernatural powers:
     * A diamond gives victory to him who carries it bound on his left
       arm, no matter the number of enemies.
     * Panics, Pestilences, enchantments, all fly before it; hence, it is
       good for sleepwalkers and the insane.
     * It deprives lodestone and magnets of their virtue (i.e., ability to
       attract iron).
     * Arabic diamonds are said to attract iron greater than a magnet.
     * A diamond's hardiness can only be broken by smearing it with fresh
       goat's blood.

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