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

Carbon occurs in nature in several allotropic forms, which are different structural arrangements of the same element [c3, t1]. Among the options provided, diamond is considered the purest form of carbon occurring in nature [t4, t6]. In a diamond crystal, each carbon atom is covalently bonded to four other carbon atoms in a rigid three-dimensional tetrahedral structure, ensuring a highly stable and pure lattice [c1, t6]. While graphite is also a pure crystalline allotrope, diamond is traditionally cited as the purest natural form [t4]. In contrast, coal is an impure form of carbon containing various organic and mineral impurities [t6]. Carbon black (soot) is an amorphous form often produced by incomplete combustion rather than being a primary natural mineral [t4, t10]. Fullerenes are also pure but are typically synthesized or found in trace amounts in specific environments like soot [t7, t8].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > Allotropes of carbon > p. 61
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > Table 3.1 > p. 40
3. [3] https://www.satheeneet.iitk.ac.in/article/chemistry/carbon-and-its-compounds/
4. [4] https://pmc.ncbi.nlm.nih.gov/articles/PMC5848992/