The obsolete term “polianite” was once used to refer to crystalline pyrolusite, which was assumed to be a different species than earthy to “crusty” pyrolusite.
The obsolete term “polianite” was once used to refer to crystalline pyrolusite, which was assumed to be a different species than earthy to “crusty” pyrolusite.
An obsolete varietal term for lepidolite.
A trioctahedral member of the true mica group. The end-member formula is KLi2AlSi4O10F2, and polylithionite forms a series with siderophyllite. Polylithionite forms as 1M, 2M2, 3T, and 2M1 polytypes and occurs in granitic pegmatites, including pegmatites at Mont St. Hilaire, Quebec, Canada, and the Kola Peninsula, Russia.
A chemical compound composed of a very large number of atoms (often hundreds or thousands) forming chains, cycles or other structures. Polymers form by a polymerization process (typically with carbon or aluminum atoms) where smaller units are bound together to form larger units. According to IUPAC, a minor change of the number of integrated atoms does not cause a significant change in the properties of the polymer, and this characteristic distinguishes polymers from oligomers. In clay science publications, oligomers are commonly mistaken for polymers.
Cf., geopolymer, oligomer, polymerization
Polymerization is a process involving a poly-condensation reaction, where smaller units of atoms are bound together to form a chemical compound composed of larger numbers of these units. The resulting compounds are called oligomers or polymers. Synthetic geopolymers (geotechnical engineering), minerals forming various interlayer oligomers in hydroxy-interlayered smectite (clay/soil science), and silicate mineral formation (metamorphic geology) are some examples that involve the polymerization processes.
Cf., geopolymer, hydroxy-interlayered minerals, oligomer, polymer
The ability of a given element or compound to crystallize in more than one form, with each form having a distinct crystal structure.
Cf., polytypism
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