Nodules are subdivided according to their internal fabric. The list presented in the key is not identical to that in the "Handbook": halo's have been deleted, as they belong to a different level, and moreover overlap with hypo-coatings, and aggregate nodules have been added, as we consider them rather as a type of internal fabric than as an external morphology, as suggested in the "Handbook".

1. nodules with a hollow interior (generally lined by euhedral crystals): geodic nodule

2. other nodules build around a foreign core: nucleic nodules

3. other nodules showing a radial pattern of cracks: septaric nodule

4. other nodules composed of several (sub)rounded entities: aggregate nodules

5. other nodules with concentric internal fabric consisting of more than one ring: concentric nodules

6. other nodules with an internal fabric pointing to a pseudomorph: pseudomorphic nodules

7. other nodules: typic nodules (check for excrements)


Combinations of characteristics are possible: e.g. nucleic nodules are often also concentric. Excrements may key out as nodules, but should be distinguished from the latter.