Refers to a structure that develops from layer-stacking sequences via polytypism.
See polytypism

An element or compound in two or more layer-like crystal structures that differs in layer-stacking sequences. Polytypism differs from polymorphism in permitting small differences in chemical composition between structures, not to exceed 0.25 atoms per formula unit of any constituent element. Layer structures that differ from one another by more than this amount are to be called polytypoids rather than polytypes. (Quot Bailey, 1977)
Cf., polymorphism

Popcorn texture is a term for a macro-texture observed on exposed and weathered clay surfaces commonly associated with deposits of sodium bentonite (usually on open-pit mine-faces, bed outcrops, or stockpiles). These high-swelling bentonites develop irregularly rounded lumps resembling mounds of popped corn caused by successive periods of swelling and shrinkage from the cyclical uptake and loss of water within the clay.
See also alligator skin texture.

A high-strength and low-absorption ceramic whiteware of high quality made from milled clay (commonly kaolin), quartz, and feldspar, fired to 1200 – 1400°C. Porcelain mainly consists of glass with some mullite. Porcelain may or may not be glazed and is commonly used as table ware, vases, electric insulators, or art ware.
Cf., ceramic, glaze

The ratio of the void volume (empty space) in a material to its total volume (i.e., including particles and the empty space between the particles), usually expressed as a percentage.
Cf., void ratio

A group of hydraulic cements composed of milled clinker usually mixed with calcium sulfate (commonly gypsum) as a set retarder. The most common Portland cement is called Ordinary Portland Cement (OPC). The name Portland cement was derived from the Isle of Portland, U.K., where Portland stone, which looked similar to cement, was quarried. Portland cement sets as a result of hydration reactions, and thus is required to be wet while curing for best stability (strength).
Cf., cement, binder, clinker

An obsolete varietal term for margarite.

An obsolete term for muscovite.

A moist, often medicated, mass applied to a wound or a painful area to reduce pain or to help in healing. The medicated mass may produce soothing vapors to aid in healing. Poultices are commonly hydrated clays, often bentonite. Poultices are also used to dissolve stains from porous decorative stone by the long-term application of a solvent via the poultice.
Syn., cataplasm

A rock or artificial material composed of amorphous SiO2 (or silica and alumina), clay minerals, carbonate phases, iron compounds, and feldspars. Pozzolan forms a binder at ambient temperatures if mixed with Ca(OH)₂ and water due to hydraulic reactions and the formation of calcium silicate hydrate (CSH) phases. Natural pozzolan is usually rich in clay minerals and soluble silica, commonly tuff with volcanic glass (silica) or sedimentary rocks with hydrated amorphous forms of silica (e.g., opal). Artificial pozzolan is often composed of milled bricks or fly ash. Pozzolan is a common additive for mortar and concrete.
Cf., calcium silicate hydrate (CSH) phases, brick, concrete, mortar