In nature, inorganic carbon is found in the Earth's crust, ~270 ppm . The isotopes found in nature are 12C (98.892 %, stable) and 13C (1.108 %, stable) .
In pure solid form, carbon exist in the following forms:
Diamond, face-centered cubic structure 
Graphite/Black lead 
Amorphous (coal, carbon black) 
Fullerenes/Buckminsterfullerenes, C60 spherical molecule 
Diamonds are found in South Africa, Zaire, the Gold Coast, Beazil, and Arkasas, USA .
Carbon in the form of graphite is mined in Mexico, Madagascar, Ceylon and Canada .