Cone-shaped graphitic whiskers (CGWs) are a form of pyrolytic carbon, consisting of conically stacked hexagonal carbon layers with an apex angle of similar to 135-140 degrees. Under transmission electron microscopy (TEM), CGWs often exhibit herringbone-striped patterns. Bright-field (BF) and dark-field (DF) TEM images indicated that the stripes are due to periodical appearance of a strong inter-planar reflection, which is consistent with helical rotation of layers with stepwise "layer overlap". High-resolution TEM revealed that the period was similar to 14-15 layers. The relationship between apex angle and stripe periodicity of CGWs could be consistently explained in terms of a helical superstructure of tightly coiled continuous graphene cone. (C) 2016 Elsevier B.V. All rights reserved.