Forms of Carbon

An element, such as carbon, can exist in several different forms, structures and arrangements, with each exhibiting different properties. These forms are called 'allotropes,' and below are some of most common allotropes of carbon.


Diamond

A rigid three dimensional lattice of carbon, it is the hardest naturally occurring substance on Earth with high dispersion of light and conductivity of heat.  Diamond is used in jewelry applications due to its beauty, as well as cutting and drilling applications due to its hardness.  Colorless diamonds are the most common in jewelry, but diamond exists in a wide variety of possible colors.  Diamond is used in high-tech applications as anvils, heatsinks, and optics. Diamond is also the best semiconductor material known to man.


Graphite

Two-dimensional sheets of carbon with weaker bonds between the sheets of carbon. Graphite is the most stable form of carbon and is electrically conductive.  Graphite is used in electrical and high-heat applications, such as nuclear reactors, in addition to common pencil lead.  It is also used as a dry lubricant, and can commonly be found as such in hardware stores.  It appears as gray microscopic sheets, but can be formed into large shapes.  High purity graphite is used in as the primary carbon source to grow diamonds in the High Pressure High Temperature (HPHT) diamond growth process.


Amorphous Carbon 

Coal, soot, or 'carbon black' are all types of amorphous carbon, which is carbon without any specific structure.  Carbon black is used in tires, printer toner and as a pigment.  Coal is primarily used as fuel in electricity generation and contains many other impurities.


Graphene

A two-dimensional honeycomb-like structure, which is essentially one single layer of graphite.  Graphene is thermally and electrically conductive and far stronger than steel of comparable thickness.  Graphene has potential applications in electronics, medical devices, and high-strength materials, though is still primarily in a research and development phase.


Carbon nanotubes

An extremely strong and hard hollow tube made with honeycomb-like carbon bonds. Carbon nanotubes are used in composite materials such as polymers, fiber sheets and epoxies.  Eventually, carbon nanotubes may be found in high-strength cables, wires, batteries, and medical devices.


Fullerenes / Buckyballs

Geodesic spheres and ellipsoids that are made entirely from carbon.  Buckyballs resemble a microscopic soccer ball.  They do not yet have any commercialized applications, but hold potential for use in medical and cancer research as well as semiconductor and solar applications.


Pyrolitic Carbon

Man-made graphite with incomplete and imperfect bonding, making it more thermally conductive than graphite.    Used in various applications for heat management, as well as a reinforcer or supplement to other materials.  Pyrolitic carbon can also be found in artificial heart valves.


Lonsdaleite

Diamond is generally cubic carbon while graphite is hexagonal carbon.  Lonsdaleite is a microscopic yellow crystal that is a rare hybrid of diamonds and graphite that is harder and denser than diamond, with the hexagonal structure of graphite. It has only been found in nature in the craters caused by massive meteor impacts and is not believed to be present in the mantle or core of the Earth, though can also be created in a lab.  Londsaleite does not currently have any known scientific or gemological applications.