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This article is about the chemical element. For other uses, see .
← carbon →
  , sometimes considered a
12.011 (12.6)
[] 2s2 2p2
Physical properties
;K (;°C, ;°F)
near 
amorphous: 1.8–2.1 g/cm3
graphite: 2.267 g/cm3
diamond: 3.515 g/cm3
;K, 10,800 kPa
graphite: 117 
graphite: 8.517 J/(mol·K)
diamond: 6.155 J/(mol·K)
Atomic properties
+4, +3, +2, +1, , , , , -4 (a mildly acidic oxide)
Pauling scale: 2.55
1st: 0;kJ/mol
2nd: 0;kJ/mol
3rd: 0;kJ/mol
sp3: 77 pm
sp2: 73 pm
sp: 69 
170 pm
Miscellanea
Crystal structure
thin rod
diamond: 18,350 m/s (at 20 °C)
diamond: 0.8 um/(m·K) (at 25 °C)
graphite: 119–165 W/(m·K)
diamond: 900–;W/(m·K)
graphite: 7.837 uΩ·m
diamond: ;GPa
diamond: 478 GPa
diamond: 442 GPa
diamond: 0.1
graphite: 1–2
diamond: 10
(3750 BCE)
Recognized as an element by
Most stable
20 min
13C is stable with 7 neutrons
Carbon (from : carbo "coal") is a
6. On the , it is the first (row 2) of six elements in column (), which have in common the composition of their outer electron shell. It is
and —making four
available to form
chemical bonds. Three
occur naturally,
being stable while
is , decaying with a
of about 5,730 years. Carbon is one of the .
Carbon is the 15th , and the
after , , and . Carbon's abundance, its unique diversity of , and its unusual ability to form s at the temperatures commonly encountered on
enables this element to serve as a common element of . It is the second most abundant element in the
by mass (about 18.5%) after oxygen.
The atoms of carbon can be bonded together in different ways, termed . The best known are , , and . The
of carbon vary widely with the allotropic form. For example, graphite is
and black while diamond is highly . Graphite is soft enough to form a streak on paper (hence its name, from the Greek verb "γρ?φειν" which means "to write"), while diamond is the hardest naturally-occurring material known. Graphite is a good
while diamond has a low . Under normal conditions, diamond, , and
have the highest
of . All carbon allotropes are solids under normal conditions, with graphite being the most
form. They are chemically resistant and require high temperature to react even with oxygen.
The most common
of carbon in
is +4, while +2 is found in
complexes. The largest sources of inorganic carbon are ,
and , but significant quantities occur in organic deposits of , , , and . Carbon forms a vast number of , more than any other element, with almost ten million compounds described to date, and yet that number is but a fraction of the number of theoretically possible compounds under standard conditions.
Theoretically predicted phase diagram of carbon
include , one of the softest known substances, and , the hardest naturally occurring substance. It
readily with other small
including other carbon atoms, and is capable of forming multiple stable
bonds with such atoms. Carbon is known to form almost ten million different compounds, a large majority of all . Carbon also has the highest
point of all elements. At
it has no melting point as its
is at 10.8 ± 0.2 MPa and 4,600 ± 300 K (~4,330 °C or 7,820 °F), so it sublimes at about 3,900 K.
Carbon sublimes in a carbon arc which has a temperature of about 5,800 K (5,530 °C; 9,980 °F). Thus, irrespective of its allotropic form, carbon remains solid at higher temperatures than the highest melting point metals such as
or . Although thermodynamically prone to , carbon resists oxidation more effectively than elements such as
that are weaker reducing agents at room temperature.
Carbon compounds form the basis of all known life on , and the
provides some of the energy produced by the
and other . Although it forms an extraordinary variety of compounds, most forms of carbon are comparatively unreactive under normal conditions. At standard temperature and pressure, it resists all but the strongest oxidizers. It does not react with , ,
or any . At elevated temperatures, carbon reacts with
to form carbon , and will rob oxygen from metal
to leave the elemental metal. This
reaction is used in the iron and steel industry to smelt iron and to control the carbon content of :
4 + 4 C(s) → 3 Fe(s) + 4 CO(g)
and with steam in the coal-gas reaction:
C(s) + H2O(g) → CO(g) + H2(g).
Carbon combines with some metals at high temperatures to form metallic carbides, such as the iron carbide
in steel, and , widely used as an
and for making hard tips for cutting tools.
As of 2009,
appears to be the strongest material ever tested. The process of separating it from
will require some further technological development before it is economical for industrial processes.
The system of carbon allotropes spans a range of extremes:
Graphite is one of the softest materials known.
is the hardest material known.
Graphite is a very good , displaying .
Diamond is the ultimate .
Graphite is a
of electricity.
Diamond is an excellent electrical , and has the highest breakdown electric field of any known material.
Some forms of graphite are used for
(i.e. firebreaks and heat shields), but some
are good thermal conductors.
Diamond is the best known naturally occurring
Graphite is .
Diamond is highly transparent.
Graphite crystallizes in the .
Diamond crystallizes in the .
Amorphous carbon is completely .
Carbon nanotubes are among the most
materials known.
Main article:
is a very short-lived species and, therefore, carbon is stabilized in various multi-atomic structures with different molecular configurations called . The three relatively well-known allotropes of carbon are , , and . Once considered exotic,
are nowadays commonly synthesized
they include , ,
and . Several other exotic allotropes have also been discovered, such as
(questionable), ,
(carbyne).
A large sample of glassy carbon.
form is an assortment of carbon atoms in a non-crystalline, irregular, glassy state, which is essentially
but not held in a crystalline macrostructure. It is present as a powder, and is the main constituent of substances such as ,
() and . At normal pressures, carbon takes the form of , in which each atom is bonded trigonally to three others in a plane composed of fused
rings, just like those in . The resulting network is 2-dimensional, and the resulting flat sheets are stacked and loosely bonded through weak . This gives graphite its softness and its
properties (the sheets slip easily past one another). Because of the delocalization of one of the outer electrons of each atom to form a , graphite conducts , but only in the plane of each
sheet. This results in a lower bulk
for carbon than for most . The delocalization also accounts for the energetic stability of graphite over diamond at room temperature.
Some allotropes of carbon: a) ; b) ; c) ; d–f)
(C60, C540, C70); g) ; h) .
At very high pressures, carbon forms the more compact allotrope, , having nearly twice the density of graphite. Here, each atom is bonded
to four others, forming a 3-dimensional network of puckered six-membered rings of atoms. Diamond has the same
and , and because of the strength of the carbon-carbon , it is the hardest naturally occurring substance measured by . Contrary to the popular belief that "", they are thermodynamically unstable under normal conditions and transform into . Due to a high activation energy barrier, the transition into graphite is so slow at normal temperature that it is unnoticeable. Under some conditions, carbon crystallizes as , a
lattice with all atoms covalently bonded and properties similar to those of diamond.
are a synthetic crystalline formation with a graphite-like structure, but in place of , fullerenes are formed of pentagons (or even heptagons) of carbon atoms. The missing (or additional) atoms warp the sheets into spheres, ellipses, or cylinders. The properties of fullerenes (split into , , and ) have not yet been fully analyzed and represent an intense area of research in . The names "fullerene" and "buckyball" are given after , popularizer of , which resemble the structure of fullerenes. The buckyballs are fairly large molecules formed completely of carbon bonded trigonally, forming
(the best-known and simplest is the soccerball-shaped C60 ). Carbon nanotubes are structurally similar to buckyballs, except that each atom is bonded trigonally in a curved sheet that forms a hollow . Nanobuds were first reported in 2007 and are hybrid bucky tube/buckyball materials (buckyballs are covalently bonded to the outer wall of a nanotube) that combine the properties of both in a single structure.
Of the other discovered allotropes,
allotrope discovered in 1997. It consists of a low-density cluster-assembly of carbon atoms strung together in a loose three-dimensional web, in which the atoms are bonded trigonally in six- and seven-membered rings. It is among the lightest known solids, with a density of about 2 kg/m3. Similarly,
contains a high proportion of closed , but contrary to normal graphite, the graphitic layers are not stacked like pages in a book, but have a more random arrangement.
has the chemical structure -(C:::C)n-. Carbon in this modification is linear with sp , and is a
with alternating single and triple bonds. This carbyne is of considerable interest to
is forty times that of the hardest known material – diamond.
In 2015, a team at the
announced the development of another allotrope they have dubbed , created by a high energy low duration laser pulse on amorphous carbon dust. Q-carbon is reported to exhibit ferromagetism, , and a hardness superior to diamonds.
Graphite ore. Penny is included for scale.
Raw diamond crystal.
"Present day" (1990s) sea surface
concentration (from the
Carbon is the
in the universe by mass after hydrogen, helium, and oxygen. Carbon is abundant in the , , , and in the
of most . Some
contain microscopic diamonds that were formed when the
was still a .[] Microscopic diamonds may also be formed by the intense pressure and high temperature at the sites of meteorite impacts.
announced a
for tracking
(PAHs) in the . More than 20% of the carbon in the universe may be associated with PAHs, complex compounds of carbon and hydrogen without oxygen. These compounds figure in the
where they are hypothesized to have a role in
and formation of . PAHs seem to have been formed "a couple of billion years" after the , are widespread throughout the universe, and are associated with
It has been estimated that the solid earth as a whole contains 730
of carbon, with 2000 ppm in the core and 120 ppm in the combined mantle and crust. Since the mass of the earth is 5.972×1024 kg, this would imply 4360 million
of carbon. This is much more than the amount of carbon in the oceans or atmosphere (below).
In combination with
in , carbon is found in the Earth's atmosphere (approximately 810 gigatonnes of carbon) and dissolved in all water bodies (approximately 36,000 gigatonnes of carbon). Around 1,900 gigatonnes of carbon are present in the .
(such as , , and ) contain carbon as well.
amount to around 900 gigatonnes with perhaps 18 000 Gt of resources.
are around 150 gigatonnes. Proven sources of natural gas are about 175 1012 cubic metres (containing about 105 gigatonnes of carbon), but studies estimate another 900 1012 cubic metres of "unconventional" deposits such as , representing about 540 gigatonnes of carbon.
Carbon is also found in
in polar regions and under the seas. Various estimates put this carbon between 500, 2500 , or 3000 Gt.
In the past, quantities of hydrocarbons were greater. According to one source, in the period from 1751 to 2008 about 347 gigatonnes of carbon were released as carbon dioxide to the atmosphere from burning of fossil fuels. Another source puts the amount added to the atmosphere for the period since 1750 at 879 Gt, and the total going to the atmosphere, sea, and land (such as ) at almost 2000 Gt.
Carbon is a constituent (about 12% by mass) of the very large masses of
and so on).
is very rich in carbon ( contains 92–98%) and is the largest commercial source of mineral carbon, accounting for 4,000 gigatonnes or 80% of .
As for individual carbon allotropes, graphite is found in large quantities in the
(mostly in
and ), , , , and . Natural diamonds occur in the rock , found in ancient
"necks", or "pipes". Most diamond deposits are in , notably in , , , the , and . Diamond deposits have also been found in , , the Russian , , and in Northern and Western . Diamonds are now also being recovered from the ocean floor off the . Diamonds are found naturally, but about 30% of all industrial diamonds used in the U.S. are now manufactured.
Carbon-14 is formed in upper layers of the troposphere and the stratosphere at altitudes of 9–15 km by a reaction that is precipitated by .
are produced that collide with the nuclei of nitrogen-14, forming carbon-14 and a proton.
Carbon-rich asteroids are relatively preponderant in the outer parts of the
in our . These asteroids have not yet been directly sampled by scientists. The asteroids can be used in hypothetical , which may be possible in the future, but is currently technologically impossible.
Main article:
of carbon are
that contain six
plus a number of
(varying from 2 to 16). Carbon has two stable, naturally occurring . The isotope
(12C) forms 98.93% of the carbon on Earth, while
(13C) forms the remaining 1.07%. The concentration of 12C is further increased in biological materials because biochemical reactions discriminate against 13C. In 1961, the
(IUPAC) adopted the isotope
as the basis for . Identification of carbon in
(NMR) experiments is done with the isotope 13C.
(14C) is a naturally occurring , created in the
and upper ) by interaction of
with . It is found in trace amounts on Earth of up to 1 part per
(0.%), mostly confined to the atmosphere and superficial deposits, particularly of
and other organic materials. This isotope decays by 0.158 MeV . Because of its relatively short
of ;years, 14C is virtually absent in ancient rocks. The amount of 14C in the
and in living organisms is almost constant, but decreases predictably in their bodies after death. This principle is used in , invented in 1949, which has been used extensively to determine the age of carbonaceous materials with ages up to about 40,000 years.
There are 15 known isotopes of carbon and the shortest-lived of these is 8C which decays through
and has a half-life of 1.98739x10-21 . The exotic 19C exhibits a , which means its
is appreciably larger than would be expected if the
of constant .
Main articles:
Formation of the carbon atomic nucleus requires a nearly simultaneous triple collision of
( nuclei) within the core of a
star which is known as the , as the products of further nuclear fusion reactions of helium with hydrogen or another helium nucleus produce
respectively, both of which are highly unstable and decay almost instantly back into smaller nuclei. This happens in conditions of temperatures over 100 megakelvin and helium concentration that the rapid expansion and cooling of the early universe prohibited, and therefore no significant carbon was created during the .
According to current physical cosmology theory, carbon is formed in the interiors of stars in the horizontal branch by the collision and transformation of three helium nuclei. When those stars die as supernova, the carbon is scattered into space as dust. This dust becomes component material for the formation of second or
systems with accreted planets. The
is one such star system with an abundance of carbon, enabling the existence of life as we know it.
is an additional fusion mechanisms that powers stars, wherein carbon operates as a .
Rotational transitions of various isotopic forms of carbon monoxide (for example, 12CO, 13CO, and 18CO) are detectable in the
wavelength range, and are used in the study of
Main article:
Diagram of the carbon cycle. The black numbers indicate how much carbon is stored in various reservoirs, in billions tonnes ("GtC" stands for
figures are circa 2004). The purple numbers indicate how much carbon moves between reservoirs each year. The sediments, as defined in this diagram, do not include the ~70 million GtC of carbonate rock and .
Under terrestrial conditions, conversion of one element to another is very rare. Therefore, the amount of carbon on Earth is effectively constant. Thus, processes that use carbon must obtain it from somewhere and dispose of it somewhere else. The paths of carbon in the environment form the . For example,
plants draw
from the atmosphere (or seawater) and build it into biomass, as in the , a process of . Some of this biomass is eaten by animals, while some carbon is exhaled by animals as carbon dioxide. The carbon cycle is considerably more complicated
for example, some carbon dioxide is dis if bacteria do not consume it, dead plant or animal matter may become
or , which releases carbon when burned.
Main article:
Structural formula of , the simplest possible organic compound.
Correlation between the carbon cycle and formation of organic compounds. In plants, carbon dioxide formed by carbon fixation can join with water in
(green) to form organic compounds, which can be used and further converted by both plants and animals.
Carbon can form very long chains of interconnecting C-C bonds, a property that is called . Carbon-carbon bonds are strong and stable. Through catenation, carbon forms a countless number of compounds. A tally of unique compounds shows that more contain carbon that those that do not.[] A similar claim can be made for hydrogen because most organic compounds also contain hydrogen.[]
The simplest form of an organic molecule is the —a large family of
that are composed of
atoms bonded to a chain of carbon atoms. Chain length, side chains and
all affect the properties of organic molecules.
Carbon occurs in all known
life and is the basis of . When united with , it forms various
that are important to industry as , , , as chemical feedstock for the manufacture of
and , and as .
When combined with oxygen and hydrogen, carbon can form many groups of important biological compounds including , , , , , and aromatic ,
and . With
it forms , and with the addition of sulfur also it forms , , and
products. With the addition of phosphorus to these other elements, it forms
and , the chemical-code carriers of life, and
(ATP), the most important energy-transfer molecule in all living cells.
Commonly carbon-containing compounds which are associated with minerals or which do not contain hydrogen or fluorine, are treated separa the definition is not rigid (see reference articles above). Among these are the simple oxides of carbon. The most prominent oxide is
(CO2). This was once the principal constituent of the , but is a minor component of the
today. Dissolved in , it forms
3), but as most compounds with multiple single-bonded oxygens on a single carbon it is unstable. Through this intermediate, though, resonance-stabilized
are produced. Some important minerals are carbonates, notably .
2) is similar.
The other common oxide is
(CO). It is formed by incomplete combustion, and is a colorless, odorless gas. The molecules each contain a triple bond and are fairly , resulting in a tendency to bind permanently to hemoglobin molecules, displacing oxygen, which has a lower binding affinity.
(CN-), has a similar structure, but behaves much like a
ion (). For example, it can form the nitride
molecule ((CN)2), similar to diatomic halides. Other uncommon oxides are
2), the unstable
(C6O6), and
With reactive , such as , carbon forms either
2) to form alloys with high melting points. These anions are also associated with
and , both very weak . With an electronegativity of 2.5, carbon prefers to form . A few carbides are covalent lattices, like
(SiC), which resembles .
Main article:
Organometallic compounds by definition contain at least one carbon-metal bond. A wide range of
major classes include simple alkyl-metal compounds (for example, ), η2-alkene compounds (for example, ), and η3-allyl compounds (for example, );
containing cyclopentadienyl ligands (for example, ); and . Many
exist (for example, ); some workers consider the
ligand to be purely inorganic, and not organometallic.
While carbon is understood to exclusively form four bonds, an interesting compound containing an octahedral hexacoordinated carbon atom has been reported. The cation of the compound is [(Ph3PAu)6C]2+. This phenomenon has been attributed to the
of the gold ligands.
in his youth
name carbon comes from the
carbo for coal and charcoal, whence also comes the
charbon, meaning charcoal. In ,
and , the names for carbon are Kohlenstoff, koolstof and kulstof respectively, all literally meaning -substance.
Carbon was discovered in prehistory and was known in the forms of
to the earliest
. Diamonds were known probably as early as ;BCE in China, while carbon in the form of
was made around Roman times by the same chemistry as it is today, by heating wood in a
covered with
to exclude air.
demonstrated that iron was transformed into steel through the absorption of some substance, now known to be carbon. In 1772,
showed that diamonds
when he burned samples of charcoal and diamond and found that neither produced any water and that both released the same amount of
per . In 1779,
showed that graphite, which had been thought of as a form of , was instead identical with charcoal but with a small admixture of iron, and that it gave "aerial acid" (his name for carbon dioxide) when oxidized with nitric acid. In 1786, the French scientists ,
and C. A. Vandermonde confirmed that graphite was mostly carbon by oxidizing it in oxygen in much the same way Lavoisier had done with diamond. Some iron again was left, which the French scientists thought was necessary to the graphite structure. In their publication they proposed the name carbone (Latin carbonum) for the element in graphite which was given off as a gas upon burning graphite. Antoine Lavoisier then listed carbon as an
in his 1789 textbook.
of carbon, , that was discovered in 1985 includes
forms such as
and . Their discoverers – ,
and  – received the
in Chemistry in 1996. The resulting renewed interest in new forms lead to the discovery of further exotic allotropes, including , and the realization that "" is not strictly .
Main article:
Commercially viable natural deposits of graphite occur in many parts of the world, but the most important sources economically are in , ,
and . Graphite deposits are of
origin, found in association with ,
in schists,
and metamorphosed
or , sometimes of a metre or more in thickness. Deposits of graphite in , ,
were at first of sufficient size and purity that, until the 19th century,
were made simply by sawing blocks of natural graphite into strips before encasing the strips in wood. Today, smaller deposits of graphite are obtained by crushing the parent rock and floating the lighter graphite out on water.
There are three types of natural graphite—amorphous, flake or crystalline flake, and vein or lump. Amorphous graphite is the lowest quality and most abundant. Contrary to science, in industry "amorphous" refers to very small crystal size rather than complete lack of crystal structure. Amorphous is used for lower value graphite products and is the lowest priced graphite. Large amorphous graphite deposits are found in China, Europe, Mexico and the United States. Flake graphite is less common and of higher qu it occurs as separate plates that crystallized in metamorphic rock. Flake graphite can be four times the price of amorphous. Good quality flakes can be processed into expandable graphite for many uses, such as . The foremost deposits are found in Austria, Brazil, Canada, China, Germany and Madagascar. Vein or lump graphite is the rarest, most valuable, and highest quality type of natural graphite. It occurs in veins along intrusive contacts in solid lumps, and it is only commercially mined in Sri Lanka.
According to the , world production of natural graphite was 1.1 million tonnes in 2010, to which China contributed 800,000 t, India 130,000 t, Brazil 76,000 t, North Korea 30,000 t and Canada 25,000 t. No natural graphite was reported mined in the United States, but 118,000 t of synthetic graphite with an estimated value of $998 million was produced in 2009.
Main article:
Diamond output in 2005
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 (see figure).
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. Today, diamonds are located in the diamond-rich density fraction with the help of , after which the final sorting steps are done by hand. Before the use of
became commonplace, the separation was do diamonds have a stronger tendency to stick to grease than the other minerals in the ore.
Historically diamonds were known to be found only in alluvial deposits in . India led the world in diamond production from the time of their discovery in approximately the 9th century BCE to the mid-18th century AD, but the commercial potential of these sources had been exhausted by the late 18th century and at that time India was eclipsed by Brazil where the first non-Indian diamonds were found in 1725.
Diamond production of primary deposits (kimberlites and lamproites) only started in the 1870s after the discovery of the Diamond fields in South Africa. Production has increased over time and now an accumulated total of 4.5 billion carats have been mined since that date. About 20% of that amount has been mined in the last 5 years alone, and during the last ten years 9 new mines have started production while 4 more are waiting to be opened soon. Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia.
In the United States, diamonds have been found in ,
and . In 2004, a startling discovery of a microscopic diamond in the United States led to the January 2008 bulk-sampling of
in a remote part of .
Today, most commercially viable diamond deposits are in , ,
and the . In 2005, Russia produced almost one-fifth of the global diamond output, reports the . Australia has the richest diamantiferous pipe with production reaching peak levels of 42 metric tons (41 46 short tons) per year in the 1990s. There are also commercial deposits being actively mined in the
( for example,
and ), Brazil, and in Northern and Western .
Pencil leads for mechanical pencils are made of
(often mixed with a clay or synthetic binder).
Sticks of vine and compressed .
A cloth of woven carbon fibres
The C60 fullerene in crystalline form
Carbon is essential to all known living systems, and without it life as we know it could not exist (see ). The major economic use of carbon other than food and wood is in the form of hydrocarbons, most notably the
(petroleum).
to produce , , and other products.
is a natural, carbon-containing polymer produced by plants in the form of , , , and .
is used primarily for maintaining structure in plants. Commercially valuable carbon polymers of animal origin include ,
are made from synthetic carbon polymers, often with oxygen and nitrogen atoms included at regular intervals in the main polymer chain. The raw materials for many of these synthetic substances come from crude oil.
The uses of carbon and its compounds are extremely varied. It can form
with , of which the most common is .
is combined with
to form the 'lead' used in
and . It is also used as a
and a , as a molding material in
manufacture, in
is used as a drawing material in , barbecue , , and in many other applications. Wood, coal and oil are used as
for production of energy and . Gem quality
is used in jewelry, and
are used in drilling, cutting and polishing tools for machining metals and stone. Plastics are made from fossil hydrocarbons, and , made by
of synthetic
is used to reinforce plastics to form advanced, lightweight .
is made by pyrolysis of extruded and stretched filaments of
(PAN) and other organic substances. The crystallographic structure and mechanical properties of the fiber depend on the type of starting material, and on the subsequent processing. Carbon fibers made from PAN have structure resembling narrow filaments of graphite, but thermal processing may re-order the structure into a continuous rolled sheet. The result is fibers with higher
than steel.
is used as the black
, artist's oil paint and water colours, , automotive finishes,
is also used as a
products such as tyres and in
compounds.
is used as an
material in applications as diverse as , , and
, and in medicine to
toxins, poisons, or gases from the . Carbon is used in
at high temperatures.
is used to reduce iron ore into iron (smelting).
of steel is achieved by heating finished steel components in carbon powder.
and , are among the hardest known materials, and are used as
in cutting and grinding tools. Carbon compounds make up most of the materials used in clothing, such as natural and synthetic
and , and almost all of the interior surfaces in the
other than glass, stone and metal.
industry falls into two categories: one dealing with gem-grade diamonds and the other, with industrial-grade diamonds. While a large trade in both types of diamonds exists, the two markets act in dramatically different ways.
or , gem diamonds do not trade as a : there is a substantial mark-up in the sale of diamonds, and there is not a very active market for resale of diamonds.
Industrial diamonds are valued mostly for their hardness and heat conductivity, with the gemological qualities of clarity and color being mostly irrelevant. About 80% of mined diamonds (equal to about 100 million carats or 20 tonnes annually) are unsuitable for use as gemstones are relegated for industrial use (known as ). , invented in the 1950s, found almost immediate ind 3 billion carats (600 ) of synthetic diamond is produced annually.
The dominant industrial use of diamond is in cutting, drilling, grinding, and polishing. Most of these applications do not re in fact, most diamonds of gem-quality except for their small size can be used industrially. 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
(see ), high-performance , and limited use in specialized . With the continuing advances in the production of synthetic diamonds, new applications are becoming feasible. Garnering much excitement is the possible use of diamond as a
suitable for , and because of its exceptional heat conductance property, as a
(photo by , 1942)
Pure carbon has extremely low
to humans and can be handled and even ingested safely in the form of graphite or charcoal. It is resistant to dissolution or chemical attack, even in the acidic contents of the digestive tract. Consequently, once it enters into the body's tissues it is likely to remain there indefinitely.
was probably one of the first pigments to be used for , and
was found to have carbon tattoos that survived during his life and for ;years after his death. Inhalation of coal dust or soot () in large quantities can be dangerous, irritating lung tissues and causing the congestive
disease, . Diamond dust used as an abrasive can harmful if ingested or inhaled. Microparticles of carbon are produced in diesel engine exhaust fumes, and may accumulate in the lungs. In these examples, the harm may result from contaminants (e.g., organic chemicals, heavy metals) rather than from the carbon itself.
Carbon generally
but carbon nanoparticles are deadly to .
Carbon may burn vigorously and brightly in the presence of air at high temperatures. Large accumulations of coal, which have remained inert for hundreds of millions of years in the absence of oxygen, may
when exposed to air in coal mine waste tips, ship cargo holds and coal bunkers, and storage dumps.
where graphite is used as a , accumulation of
followed by a sudden, spontaneous release may occur.
to at least 250 °C can release the energy safely, although in the
the procedure went wrong, causing other reactor materials to combust.
The great variety of carbon compounds include such lethal poisons as , the
from seeds of the
(CN-), and such essentials to life as
Core organic chemistry
Many uses in chemistry
Academic research, but no widespread use
Bond unknown
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