a) The formation of a stable dispersion of colloidal particles in water, usually by chemical additives;
b) In bentonite clay-product manufacturing, the use of chemical additives to improve the performance characteristics of the clay for a particular end use.
Cf., peptized clay.
A clay to which chemicals have been added to improve the performance characteristics of the clay for a specific end use.
Cf., peptize
As applied to clay science, percutaneous migration refers to the diffusion of elements from clay poultices (peloids) through the skin.
Replacement of a reactant mineral by a product mineral beginning at the outermost margin of the reactant mineral’s grain or fracture-bounded remnants.
See centripetal replacement.
An obsolete term for margarite.
Hydrated volcanic glass containing 2-5 wt. % H2O. Because of their high viscosity, rhyolitic melts form glasses upon cooling. Devitrification produces a “perlitic structure”, which is characterized by concentric cracks. Perlite has a pearly luster, and is glassy gray to black. When heated, H2O is released and glass shards dehydrate and expand to volumes to 20 times their original size. Associated zeolites are common. Perlite, after heating, is used as aggregate, fillers, in plaster products and in light-weight concrete, as coatings for steel beams as fire protection to reduce the possibility of melting or partial melting, etc.
In soil science, permeability is a property of a soil or porous medium, which expresses the ease of a fluid flow (e.g., water, crude oil, gas, or air) through the medium, given in units of (length)2. In contrast, hydraulic conductivity refers specifically to water as the permeant.
Cf., hydraulic conductivity
See astrophyllite group.
An optical (transmitted visible light) microscope with polarizing filters or prisms along the optical path. The petrographic microscope is commonly used to examine thin sections and grain mounts.
See thin section, crossed Nichols, plane light.
The negative logarithmic (log10) measure of hydrogen ion (H+) activity which defines the acidity or alkalinity of a solution. In pure water, a value of 7 is neutral and represents an exact balance between the activities of hydrogen (H+) and hydroxide (OH–) ions. Values lower than 7 represent an increase in hydrogen ion activity and are acidic. Values higher than 7 represent a decrease in hydrogen ion activity and are alkaline.