Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
by Blake Gurtler
Carbon exists in several different forms. These
forms are referred to as “carbon allotropes” since an allotrope is when an
element exists in several structural forms despite being the same element in the
same state. Two of the most well-known allotropes of carbon are diamonds and
graphite, both consist of pure carbon the only difference being how the atoms
are bonded with each other.
When carbon covalently bonds in a tetrahedron shape
it results in diamond being formed. This unique formation of carbon gives its
qualities. Diamond is the hardest known natural mineral. Diamond acts as a good
conductor of heat but acts as an insulator for electricity. Common industrial
uses for diamond include drilling and grinding.
Graphite is formed by carbon atoms creating a layer
of honey comb lattices this arrangement of carbon atoms results in graphite
being the most stable form of carbon. Graphite is much more brittle than
diamond and acts as an electrical conductor instead of an insulator. This has
resulted in graphite being used for electrodes and as a dry rub for industrial
Amorphous carbon is a term used to refer to carbon that does not have a crystalline structure. Amorphous carbon often has bits of either graphite or diamond in it. Coal is often referred to as amorphous carbon though the process of creating coal is the degradation by heat which does not create true amorphous carbon.
Buckminster fullerene is the most common form of carbon fullerene molecule. Fullerene refers to a carbon molecule that is spherical, hollow, or tube shaped in nature. A spherical fullerene is also referred to as a buckyball. Fullerenes have been a hot topic in science and will most likely continue to be an area of research for some time to come. Fullerenes are fairly stable but are not completely unreactive as far as chemical reactions go. Fullerenes are semi soluble.
Carbon fibers are made by combining many carbon atoms in a crystalline pattern in a small space. The crystallized shape on the atomic level gives the fiber similar characteristics to diamonds in that they fibers are incredibly strong for their small size. The carbon fibers are then usually combined with other materials such as plastics to give the new composite different properties depending on the project.