Bauxitic horizon
One which contains more than 20% (visual abundance estimate) of bauxite nodules or concretions which are mostly uncemented, and has a minimum thickness of 0.1 m.
Bauxite is an impure mixture of hydrous aluminium oxides and hydroxides with variable levels of iron. Distinguishing by eye between bauxitic nodules or concretions and ferruginous forms cannot be undertaken with any confidence.
Elemental analysis is required to determine if there is sufficient aluminium present (>35%) to confidently conclude the nodules or concretions are bauxite. Identification can also be made with more confidence if the horizon occurs within soils in the vicinity of bauxite mine sites or from the same geological formations known to be bauxite rich.