What is Graphite?- Definition, Types, and Uses

Graphite is one form (allotrope) of the element carbon. In graphite, carbon atoms are arranged in layers. This layering gives graphite many of its properties.

Graphite can be found naturally or may be created synthetically. Naturally occurring deposits of graphite (formed through a combination of igneous and metamorphic physical processes) are mined in a number of different countries, including China, Madagascar, Brazil and Canada.

Synthetic graphite is made by heating a variety of carbon containing substances (including petrochemicals, pitch, coal or acetylene).

When super-heated (to temperatures higher than 4000°C) the carbon atoms rearrange themselves into layers to form graphite. Synthetic graphite is recognized to have greater purity than naturally occurring graphite.

What is Graphite?

Graphite is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions.

Synthetic and natural graphite are consumed on a large scale (1.3 million metric tons per year in 2022) for uses in pencils, lubricants, and electrodes. Under high pressures and temperatures, it converts to diamond. It is a good (but not excellent) conductor of both heat and electricity.

Graphite has a layered structure that consists of rings of six carbon atoms arranged in widely spaced horizontal sheets.

Graphite thus crystallizes in the hexagonal system, in contrast to diamond, another form of carbon, that crystallizes in the octahedral or tetrahedral system. Such pairs of differing forms of the same element usually are rather similar in their physical properties, but not so in this case.

What is Graphite

Who discovered graphite?

Graphite was first accidentally synthesized by Edward G. Acheson when he was doing high-temperature experiments with carborundum. He found that at around 4,150°C (7,500°F) the silicon in the carborundum evaporates and the carbon remains in graphitic form.

Acheson was granted a patent for graphite production in 1896, and commercial production began in 1897. Since 1918, petroleum coke, small and imperfect graphite crystals surrounded by organic compounds, has been the primary raw material for the production of 99 to 99.5 percent pure graphite.

What color is graphite?

Graphite is a naturally occurring form of carbon that is typically gray or black in color. It is one of the three allotropic forms of carbon, along with diamond and amorphous carbon.

The color of graphite can vary depending on its purity and the presence of impurities. Pure graphite is typically dark gray or black, while impure graphite may be lighter in color due to the presence of other minerals or contaminants.

Graphite that is used in high-temperature applications, such as in furnace linings, may also be pink or reddish in color due to the presence of impurities.

In summary, graphite is typically gray or black in color, although its exact shade can vary depending on its purity and the presence of impurities.

Structure of Graphite

Graphite has a layered structure that consists of rings of six carbon atoms arranged in widely spaced horizontal sheets. Graphite thus crystallizes in the hexagonal system, in contrast to the same element crystallizing in the octahedral or tetrahedral system as diamond.

Graphite consists of layers of carbon atoms arranged in 6-membered, hexagonal rings. These rings are connected to one another at their edges. Layers of fused rings can be modeled as an infinite series of fused benzene rings (without hydrogen atoms).

Structure of graphite
The Structure of Graphite

Carbon atoms in these ring arrangements are in the sp2 hybridized state. In the sp2 molecular orbital model, each carbon atom is bound to three other species, in the case of graphite three more carbon atoms. In this bond mode, the bond angle between adjacent carbon atoms is 120.

These “ring arrays” are arranged in large layers of carbon atoms, and individual layers are called graphene layers. The carbon-carbon bond length in a layer plane is 1.418.

Graphite layers are stacked on top of each other parallel to the crystallographic “C” axis of the hexagonal 4-axis system in which graphite crystallizes. For more information about graphite structure please visit our guide.

Properties of Graphite

Graphite is an allotrope of carbon that is used for making moderator rods in nuclear power plants. Its properties are as follows:

  • A greyish-black, opaque substance.
  • Lighter than diamond, smooth and slippery to the touch.
  • A good conductor of electricity (Due to the presence of free electrons) and a good conductor of heat.
  • A crystalline solid
  • Very soapy to the touch.
  • Non-inflammable.
  • Soft due to weak Vander wall forces.
  • The conductor of electricity.

physical properties of graphite

Graphite has a high melting point, similar to that of a diamond. To melt graphite, it is not enough to loosen one sheet from another. You have to break the covalent bond throughout the structure.

It is soft and slippery to the touch and is used in pencils and as a dry lubricant for things like locks. You can think of graphite more like a pack of cards – each card is strong, but the cards slide on top of each other or even fall off the pack altogether. When you use a pencil, the sheets will rub off and stick to the paper.

Also, it has a lower density than diamonds. This is due to the relatively large amount of space that is “wasted” between the sheets.

It is insoluble in water and organic solvents – for the same reason that diamond is insoluble. The force of attraction between solvent molecules and carbon atoms will never be strong enough to overcome the strong covalent bonds in graphite.

Graphite conducts electricity. The delocalized electrons can move freely through the sheets. When a piece of graphite is tied into a circuit, electrons can fall off one end of the sheet and be replaced with new ones at the other end.

Chemical properties of Graphite

ColorIron-black to steel-gray; deep blue in transmitted light
Chemical ClassificationNative element
StreakBlack
LusterMetallic, sometimes earthy
DiaphaneityOpaque
CleavagePerfect in one direction
Mohs Hardness1 to 2
Specific Gravity2.1 to 2.3
Diagnostic PropertiesColor, streak, slippery feel, specific gravity
Chemical CompositionC
Crystal SystemHexagonal

Types of Graphite

The Different Types of Graphite:  

  1. Natural Graphite
  2. Synthetic Graphite.

#1. Natural Graphite.

Natural graphite is a mineral composed of graphitic carbon. It varies considerably in crystallinity.

Most of the commercial (natural) graphites are mined, and typically contain other minerals. After graphite is mined, it usually requires a considerable amount of mineral processing like froth flotation to concentrate the graphite.

Natural graphite is an excellent conductor of heat and electricity, stable over a broad range of temperatures, and a highly refractory material with a high melting point of 3650 °C.

There are three types of natural graphite:

  • Crystalline Vein Graphite
  • Amorphous Graphite
  • Flake Graphite

1.1 Crystalline Vein Graphite.

Vein graphite, also known as lump graphite, is believed to have hydrothermal origins. It occurs in fissures or fractures and appears as massive platy intergrowths of fibrous or needle-like crystalline aggregates.

The size, shape, and purity of vein graphite vary depending on the conditions under which the original material was metamorphosed. Compared to flake and amorphous graphite, vein graphite has a higher carbon content and is the most desirable type of graphite.

Uses: Vein graphite is used in a variety of applications, including refractories, ceramics, lubricants, batteries, and steelmaking. It is also an ideal material for use in electrical applications because of its high carbon content and conductivity.

Investor Insight: Vein graphite is the most valuable type of graphite, and the global market is expected to grow exponentially in the coming years.

Like flake graphite, the market for vein graphite is driven by factors such as the increasing demand for EVs and the need for energy storage solutions.

1.2 Amorphous Graphite

Amorphous graphite is the least graphitic of the three main types. It forms when carbonaceous material undergoes low-grade metamorphism, meaning that the original material was not heated to a high enough temperature for long enough to form crystals.

Amorphous graphite is typically found as small, dark particles in sedimentary rocks like coal and shale.

Uses: Although it has a lower carbon content than flake and vein graphite, amorphous graphite is still used in some industrial applications because it can be mined relatively easily and doesn’t require extensive processing; amorphous graphite is often used in lubricants, pencils, batteries, and brake pads.

Investor Insight: Because amorphous graphite is less graphitic and has a lower carbon content, it’s not as valuable as the other types of graphite.

However, it can still be profitable to mine amorphous graphite if there is a market for the products it’s used in nearby.

The purity of amorphous graphite that is marketable today is generally between 70 and 90 percent, according to experts.

1.2 Flake Graphite

Flake graphite forms when carbonaceous material is subjected to high-grade metamorphism. This type of graphite has a higher carbon content than amorphous graphite and typically forms in flakes or plates.

The size, shape, and purity of the flakes vary depending on the conditions under which the original material was metamorphosed.

Uses:  Flake graphite is the most widely used type of graphite. Its applications include everything from pencils and lubricants to batteries and solar panels. In fact, flake graphite is a key component in lithium-ion batteries, which are used in electric vehicles (EVs).

Investor Insight: Because of its wide range of applications, flake graphite is a valuable commodity. The global market for flake graphite is expected to grow at a rate of 1.10% for the forecast period of 2021 to 2028, according to Data Bridge Market Research.

#2. Synthetic Graphite

Synthetic graphite can be produced from coke and pitch. Although this graphite is not as crystalline as natural graphite, it is likely to have higher purity. There are basically two types of synthetic graphite.

One is electrographite, pure carbon produced from coal tar pitch and calcined petroleum coke in an electric furnace. The second is synthetic graphite, produced by heating calcined petroleum pitch to 2800 °C.

Essentially, synthetic graphite has higher electrical resistance and porosity, and lower density. Its enhanced porosity makes it unsuitable for refractory applications.

Synthetic graphite contains mainly graphitic carbon that has been attained by graphitization, heat treatment of non-graphitic carbon, or chemical vapor deposition from hydrocarbons at temperatures over 2100 K.

Uses of Graphite

Graphite has been used since ancient times. It has a wide range of applications in the modern world too.

Let’s look at some common uses of graphite below:

  • Writing Materials
  • Lubricants
  • Refractory
  • Nuclear Reactors
  • Batteries
  • Graphene Sheets

1. Writing Materials

The word graphite is from the Greek language which translates as ‘to write’. So the most common use of graphite is in making the lead in pencils. This lead is a mixture of clay and graphite which is in an amorphous form.

2. Lubricants/Repellents

Graphite is one of the main ingredients in lubricants like grease, etc. This mineral reacts with atmospheric water vapor and creates a thin film or layer over the surface applied and thus reducing friction. Graphite is also used in car brakes and clutches.

The powdered form of lump graphite is also used in paints. Why? Well, graphite by nature is water-repellent. So it offers a protective coating on wood and other surfaces.

3. Refractories

Due to its high tolerance to heat and unchangeability, Graphite is a widely used refractory material. It finds its use in the manufacturing industry and it helps in the production of glass and steel as well as the processing of iron.

4. Nuclear Reactors

Graphite can absorb fast-moving neutrons. As a result, it is used in reactors to stabilize nuclear reactions.

5. Electrical Industry

Crystalline flake graphite is used in the manufacturing of carbon electrodes, brushes, and plates needed in dry cell batteries and the electrical industry.

Interestingly, natural graphite is also processed into synthetic graphite. This type of graphite is useful in lithium-ion batteries.

6. Graphene Sheets

Graphite can be used to make graphene sheets. These sheets are said to be 100 times stronger and 10 times lighter than steel.

This derivative of graphite is further used in making lightweight and strong sports equipment. Many are considering future applications in the field of the medical and aerospace industry.