While cerium anomalies in coal are usually negative, they can rarely be positive as well. This can occur during volcanic eruptions when volcanic ash is weathered into mafic tuffs with positive Ce-anomalies. The Pavlovka deposit in Far East Russia has large positive Ce-anomalies in its Fe-Mn oxyhydroxide ores. Because cerium is one of only two REEs that can obtain an oxidation number of +4, Ce is absorbed into Mn(IV) oxides instead of other REEs and this results in a positive Ce-anomaly.