As which one of the following, does carbon occur in its purest form in nature ?

Carbon exists in nature in several allotropic forms, primarily diamond, graphite, and amorphous forms like coal [t9]. Diamond is considered the purest form of carbon in nature because it consists of a rigid, three-dimensional tetrahedral structure where each carbon atom is covalently bonded to four others, leaving no free electrons or significant impurities in its crystal lattice [t3][t6]. While graphite is also a crystalline allotrope and the most thermodynamically stable form [t5], it often contains trace impurities in natural deposits. Coal is a complex mixture containing carbon along with hydrogen, nitrogen, oxygen, and sulfur, making it an impure form [c3][c4]. Carbon black is a synthetic amorphous form produced by incomplete combustion [t6]. Although fullerenes are sometimes cited as the purest allotrope due to their unique molecular structure, they are not the primary natural form found in significant quantities compared to diamond [t7].

Sources

1. [1] https://winter.group.shef.ac.uk/webelements/carbon/
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > 4.2 VERSATILE NATURE OF CARBON > p. 62
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > p. 58