An obsolete term for pyrophyllite or a mixture with dominant pyrophyllite.
An obsolete term for pyrophyllite or a mixture with dominant pyrophyllite.
Palliative refers to the relief of pain (or more generally, other side effects of an illness), but without treatment of the underlying condition. Clay baths (balnea) are commonly used as a palliative treatment for chronic pain (e.g., arthritis).
A member of the palygorskite-sepiolite group with a composition of approximately (Mg5-y-zR3+yvz) (Si8-xR3+x) O20 (OH)2 (OH2)4 . R2+(x-y+2x)/2 (H2O)4, where R are cations, v are vacancies, and x, y, and z are compositional parameters.
See palygorskite-sepiolite group
The palygorskite-sepiolite group consists of palygorskite, sepiolite, falcondoite, kalifersite, loughlinite, raite, tuperssuatsiaite, yofortierite, windhoekite, and an un-named species, ~NaCa(Fe2+, Al, Mn)5[Si8O19(OH)](OH)7.5H2O. Palygorskite and yofortierite are dioctahedral and all others are trioctahedral. The palygorskite-sepiolite group has infinitely extending tetrahedral sheets involving 6-fold rings of tetrahedra. Tetrahedral sheets have a continuous basal oxygen-atom plane, but the palygorskite-sepiolite group has apical oxygen atoms pointing in opposing directions within a continuous sheet. Each section of like-pointing tetrahedra form a strip or ribbon pattern, and each ribbon consists of a tetrahedral ring (or two pyroxene-like chains) in palygorskite and 1.5 rings (or three pyroxene-like chains) in sepiolite. In palygorskite and sepiolite, the octahedra, which are linked via edge sharing, form strips that are not continuous sheets. In sepiolite, the octahedral strips are eight octahedra wide, whereas strips that are five octahedra in width occur in palygorskite. The terminal anion at the edges of the octahedral strip involves four OH2 groups per formula unit and are required for charge balance. Because these groups are well bonded to the octahedral metal cation and not isolated, they are not referred to as H2O. Vacant regions, zeolitic H2O, and exchangeable cations may reside in the channels formed at the edges of the octahedral strips in palygorskite and sepiolite. Exchange reactions with organic molecules are possible if the size of the organic cations is appropriate, because steric constraints control what can enter this channel. Larger molecules also may be adsorbed by the structure, but this is probably because of defects. Environments of formation range from low-temperature aqueous solutions to high-temperature hydrothermal (< 350 oC) conditions, and natural solutions tend to be alkali-rich with (Na + K)/Al > 1. See individual species for chemical compositions.
A name introduced to replace palygorskite-sepiolite. This name has not been accepted by the International Mineralogical Association (or any nomenclature committee) and therefore should not be used.
A pedofeature formed by fragments of laminated clay coatings.
See pedofeature.
A dioctahedral member of the true mica group. The end-member formula is NaAl2vAlSi3O10(OH)2, where v = vacancy, and thus paragonite is the Na analogue of muscovite. The typical range in composition is: K < 0.5, Ca ≤ 0.11. (Rieder et al., 1998). Paragonite occurs as 2M1, 3T, and 1M polytypes. Paragonite is found in low- and medium-grade metapelites and at variable pressures near those of greenschist and blueschist facies. It commonly occurs with muscovite/phengite and margarite.
Cf., muscovite.
A weak magnetic attraction that develops in the presence of an external magnetic field and this attraction occurs when magnetic moments align in the material. When the magnetic field is removed, the magnetic moments (thermally) randomize and the magnetic behavior disappears. Paramagnetism is found in substances with atoms/molecules possessing an odd number of unpaired electrons. Hence, transition metals with partly filled 3d orbital electronic shells may show paramagnetic behavior. Thus, metals (e.g., Ti) and compounds (e.g., fayalite, augite, annite) may be paramagnetic.
Cf., magnetic susceptibility
Hydrated clays mixed with paraffin, heated to 40-45
A modulated 2:1 layer silicate with continuous Mn-rich octahedral sheets and 6-fold tetrahedral rings forming islands three rings wide. These islands have inter-island linkages, some of which have inverted tetrahedra, involving 12-fold tetrahedral rings and double four-member rings, which act to link adjacent tetrahedral sheets (Eggleton and Guggenheim, 1994). A structural formula for parsettensite is M7.5(Mn,Mg)49(Si64.5Al7.5)Σ=72O168(OH)50 . nH2O. Parsettensite occurs in (low grade to very low grade) metasedimentary manganese ore deposits in Val d’Err, Oberhalbstein, Graubünden, Switzerland and on surfaces of pegmatite minerals by either hydrothermal or pneumatalytic processes at the Foote mine, Kings Mountain, North Carolina, USA, and in a very low grade metagraywacke and argillite near Otago, New Zealand.
Cf., stilpnomelane