Icacinicarya amygdaloidea is one of the largest London Clay fruits placed in this form-genus. The known endocarps are long and almond-like, around 33–35 mm in length, with a flattened lenticular cross-section. Their large size and elongate proportions set them apart from the compact, subglobose or short-oval stones that dominate many other Icacinaceae in the flora.

Only a very small amount of material is known and the specimens are preserved as strongly compressed carbonaceous endocarps rather than the more typical three-dimensional pyrite-permineralised stones. That preservation made micro-CT uninformative, so the modern revision accepted the species using the original morphological documentation and later comparative work. The locule lining lacks papillae. Because no foliage or stems are associated, the exact form and ecology of the plant remain unknown beyond its placement among woody icacinaceous angiosperms.