A continuous anisotropic phase formed by coalescence of mesophase spheres. Bulk mesophase retains fluidity and is deformable in the temperature range up to about 770 K, and transforms into green coke by further loss of hydrogen or low-molecular-weight species. This bulk mesophase can sometimes be formed directly from the isotropic pitch without observation of intermediate spheres.
Source:
PAC, 1995, 67, 473. 'Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)' on page 478 (https://doi.org/10.1351/pac199567030473)