This addendum extends the original algorithm (Shagarova, 2026) for the geochemical diagnostics of coal genotypes and critical metal potential. Analysis of new datasets from Greece, Nigeria, Spain, and the USA reveals that coals formed in organic-rich coastal environments—characterized by high V–Ni and V–Al correlations (r > 0.8) and low Ti/Al ratios ( 0.5%): Sb×U 0.30 → III–IV· Lignites and subbituminous coals (Ro 10 → III–IV The validity of the Type 13 approach is demonstrated through case studies from four regions, with 100% agreement between geochemical diagnosis and petrographic data. Three subtypes are defined: · 13a1 (bituminous, Ti/Al 0.1) using Ti‑normalization with silicate subtraction This refinement enhances the algorithm's applicability to paralic and high‑organic basins without requiring petrographic analysis. An updated classification table and diagnostic workflow are provided.
Olga Shagarova (Mon,) studied this question.