drop in pH to below 4 if exposed to prevailing oxidising conditions. By definition, hyposulfidic material does not convert to sulfuric material upon oxidation. In contrast to both hyposulfidic and hypersulfidic materials, monosulfidic material contains high concentrations of detectable monosulfides (≥ 0.01% acid volatile sulfide) (e.g., greigite and mackinawite). Note that monosulfidic material has not replaced Monosulfidic Black Ooze (MBO), which is now considered a type of monosulfidic material. The terms ‘sulfidisation’ and ‘sulfuricisation’ were coined to refer to the formation of sulfidic and sulfuric material, respectively. Although the terms have not been formally adopted in the ASC, their use is encouraged in Australia. However, the terms should not be used synonymously with other terms that also refer to the formation or transformation of sulfides (e.g., pyritization). Similarly, 'sulfidic material' should not be used interchangeably with similar terms such as pyritic/sulfidic sediment, rock and regolith, which may be found in publications on Acid Rock systems. The very broad term 'sulfidic geomedia' could be used to refer to both sulfidic material and pyritic/sulfidic sediment, rock and regolith; but it has no formal definition in Australia and should not be used in lieu of 'sulfidic material'. 'Self-Neutralising' Acid Sulfate Soils The term 'self-neutralising' acid sulfate soils has been used (primarily by environmental consultants) to refer to sulfidic material which does not become acidic (i.e., pH < 4) after exposure to prevailing oxidising conditions due to the presence of alkaline materials (e.g., marine carbonates) that neutralise acidity generated by the oxidation of sulfidic material. The use of this term is discouraged as it can give the impression that the soil does not pose a threat to environmental and community health. Although the aerobic weathering of hyposulfidic material does not produce excess acidity, it typically generates a saline solution containing environmentally hazardous concentrations of metals and metalloids.Therefore, 'hyposulfidic material' should be used instead of 'self-neutralising acid sulfate soil'. Australian Guidance and Other Resources Overview An array of technical manuals, maps, databases, and other forms of guidance for identifying, sampling, and/or managing acid sulfate soils have been published by Federal and State/Territory governments over the years. National Acid sulfate soils guidance: a synthesis provides a summary of available guidance. It is recommended that those not familiar with available guidance first consult this document. An overview is also available on the Commonwealth Water Quality Australia website. Key, publicly available resources are described below. National Acid Sulfate