Dear Student
Allotropy is the existence of an element in several different physical forms. In the wide form the allotropes are classified into :
A) Crystalline form
B) Amorphous form
Diamond, graphite and fullerene, Carbon nanotube (CNT) are the crystalline form of carbon allotropes.
While Coal, coke, charcoal are the amorphous form of carbon allotropes.
Regards