Graphene is not an allotrope of carbon. Allotropy is the property of some chemical elements to exist in two or more different forms, or allotropes, when found in nature. So, allotropes are basically different forms of a chemical element found in its natural state. There are several allotropes of carbon, namely (a) diamond, (b) graphite, (c) lonsdaleite, (d) C60 (Buckminsterfullerene or buckyball), (e) C540, (f) C70, (g) amorphous carbon, and (h) single-walled carbon nanotube or buckytube.