There are eight different allotropes of carbon. These are diamonds, graphite, buckyball, amorphous carbon, buckminsterfullerene, lonsdaleite, buckytube, and carbon nanotube.
Diamonds are, of course, the best known. They are used in jewelry, and decorations, and are highly prized for their clarity and their value. There is a substantial market for diamonds, and this is unlikely to change in the future.
Diamonds are also used for construction in drill bits, and for fine cutting and polishing purposes. They can be used in their hardened form, but they are also ground down to powders to be used as well.
Graphite is one that is also extremely common. It is used in pencil lead, as well as in electricity. Graphite is considered one of the most stable forms of carbon.
Amorphous carbons are more common in soot and coal. While there are some instances of whole amorphous carbons, they are not common.
Buckminsterfullerenes are molecules made entirely of carbon, and present in various sizes. They can be viewed as hollow spheres or tubes.
Buckyballs are spherical fullerenes and are associated with the buckminsterfullerenes.
Lonsdaleite is a hexagon shaped allotrope of the diamond. It is believed to be formed when the heat from the earth atmosphere comes into contact with the graphite. It does not, however, change its shape while falling.
Buckytubes and Carbon Nanotubes are cylindrical carbon allotropes that are perfect for use in electronics and many forms of technology.
While comprised of carbons, these different allotropes show the many different uses on how carbon is essential, and rightfully one of the highest used elements.