The pure form of carbon is

Carbon exists in several allotropic forms, which are different structural configurations of the same element. The primary pure forms of carbon are its crystalline allotropes: diamond, graphite, and fullerenes [2]. While diamond and graphite are infinite lattices, fullerenes like C60 are discrete molecular species [2]. Among the options provided, fullerene is often cited as the purest form of carbon because it consists of a specific, discrete number of carbon atoms (like C60) forming a hollow cage structure, which can be synthesized with extremely high purity without the surface terminations or impurities often found in the infinite lattices of diamond or graphite [1]. In contrast, charcoal is an amorphous form of carbon that contains various impurities and is not considered a pure allotrope. Therefore, fullerene is the most accurate choice for the pure form of carbon in this context.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > Allotropes of carbon > p. 61
2. [2] https://winter.group.shef.ac.uk/webelements/carbon/