Through experimentation, scientists concluded that fullerene exists in interstellar space and in soot from the burning of certain gases on Earth. In 1992 it was found for the first time in rock sediments formed more than 600 million years ago. Because fullerene is unstable when exposed to air it is not found in large quantities naturally. The synthesis of carbon-containing compounds starts from carbon compounds available in nature. Limestone, from which carbon-containing calcium carbide and acetylene can be made, is extremely important to the chemical industries in countries that have no native petroleum.
Carbon compounds containing boron and silicon are among the hardest substances known.
These carbides are used as abrasives on emery wheels. They are chemically inert and nearly indestructible. Carbides formed by the more metallic elements such as iron, cobalt, and nickel, in contrast, are easily decomposed by acids to give hydrocarbons, chiefly methane and hydrogen. Each time a neutron hits, it drives a proton from the nitrogen atom' s nucleus and takes its place. Since the atom now has six protons, it is an atom of carbon.