An obsolete term for clintonite.

An obsolete term for clintonite.

Direct precipitation of a solid phase within a solution and not on the surface of another phase.

A reaction that involves only one physical state (i.e., solid, liquid, gas).
Cf., heterogeneous reaction

See hydrotalcite group.

A mining term, now obsolete and not used in the geologic literature, that refers to the palygorskite-sepiolite group (Brindley and Pedro, 1970; Bailey et al., 1971a).

A term used in industry referring to palygorskite and/or sepiolite. This term should not be used in the scientific literature.

A poorly defined material, found as infillings in cavities in basic igneous rocks, possibly an altered chlorite or a chlorite + smectite mixture.

Humic acids are chemically diverse acids that result from the decay of plants and microorganisms in some soils, sediments, peats, coals, shales, and surface waters. These acids are insoluble in water at low pH, can be precipitated at a pH = 1, and extracted from solids using a strong base, such as NaOH or KOH.
Cf., fulvic acid, humic substances, humification, humin

The general term that includes (large-molecule) humic acid, fulvic acid, and humin, all of which form the natural organic matter (NOM) of some soils, sediments, peats, coals, and shales. Non-humic materials, such as amino acids, peptides, and sugars, may also be present in some soils as NOM. Humic substances impart the brown or black color to some soils and surface waters as well as biological productivity. Humic substances do not further biodegrade readily. Humic substances are quite heterogeneous and complex, and studies often provide average properties and chemical compositions. However, Lehmann and Kleber (2015) have suggested that large-molecule humic substances do not actually exist in soils, and NOM form from a progressive breakdown of organic compounds.
Cf., fulvic acid, humic acid, humification, humin