An adjective that describes a rock or sediment that contains clay.
An adjective that describes a rock or sediment that contains clay.
The powder X-ray diffraction pattern of fine-grained chlorite was used to obtain information about apparent chlorite “crystallinity” by M. Frey (Frey, 1987) and others, and by Arkai (1991) to correlate the reactions involving smectite-muscovite and smectite-chlorite with the Kübler index (and other metamorphic grade-indicating characteristics). Because diffraction patterns are affected by the presence of a diversity of defects, mean crystallite sizes, and other features, it is unclear if “crystallinity” is actually being measured and thus, the index should not be characterized as a “crystallinity” index.
Cf., crystalline, crystallinity index, Hinckley index, Kübler index
A modulated 2:1 layer silicate with a continuous octahedral sheet containing Mn and Na and tetrahedral sheets having 5-, 6-, 7-, and 8-fold tetrahedral rings (Yakovenchuk et al., 2007). One symmetry-unique Si tetrahedron is inverted relative to the others in the sheet and this tetrahedron links two adjacent tetrahedral sheets. The other tetrahedra link to the octahedral sheets. The ideal chemical composition is K5Na6Mn3+Mn2+14(Si9O22)4(OH)10 . 4H2O. Armbrusterite is found in the Khibiny alkaline massif, Kola Peninsula, Russia.
Cf., bementite, parsettensite, pyrosmalite, innsbruckite, varennesite
A formula describing the temperature dependence of a rate constant (k) for a chemical reaction: k = Ae-Ea/RT where Ea is the activation energy, R is the ideal gas constant and T is the temperature (Kelvin). A is the pre-exponential factor.
Minerals with the same shape characteristics as asbestos.
Cf., aspect ratio, asbestos, asbestosis.
A general commercial term for two fibrous silicate-mineral groups: chrysotile, the fibrous serpentine mineral, and fibrous amphiboles (amosite, crocidolite, anthophyllite, tremolite, and actinolite) and these two groups are considered hazardous by U.S. regulatory agencies (e.g., Occupational Safety and Health Administration, OSHA). Asbestos minerals are incombustible, make excellent thermal and electrical insulators, resist chemical attack, and have high tensile strength. In addition to being fibrous, other characteristics include flexibility and the ability of fibers to be separated (often capable of being woven). The aspect ratio (i.e., length-to-width ratio) is often defined (as stated within Federal Register, June 8, 1992) as at least 20:1 (and often greater than 100:1) by mining or stone companies. Actinolite and tremolite have no commercial value. Amosite (“brown asbestos”) is a variety of grunerite (along the cummingtonite-grunerite join) whereas crocidolite (“blue asbestos”) is a variety of riebeckite. Asbestos minerals have been implicated as pathogenic when inhaled, although the minerals are not equally pathogenic with chrysotile, which is considerably less dangerous than the amphiboles. OSHA (Federal Register, June 8, 1992) considers asbestos fiber dimensions as the best indicator of significant “fiber pathology”. OSHA considers fiber-dimension lengths most pathologically active at greater than 5 micrometers and these fibers generally have aspect ratios of greater than 10:1 with most greater than 20:1.
Cf., aspect ratio, asbestiform, asbestosis
Asbestosis is a disease that results in fibrosis of the lung from the inhalation of asbestiform particles, such as fibrous serpentine (chrysotile) and fibrous amphibole (crocidolite, amosite, anthophyllite, tremolite, actinolite), which can lead to mesothelioma (cancer). The amphiboles have a much greater residence time in the lung than the serpentines, which dissolve more readily at the pH of lung tissue (Hume and Rimstidt, 1992; Werner et al., 1995). See asbestos, asbestiform.
Cf., asbestiform, asbestos, aspect ratio
The aspect ratio is the ratio of the smallest dimension to the longest dimension. For fibers, the aspect ratio is the ratio between the width to the length. NIOSH defines asbestos, for example, with a length:width ratio (also commonly referred to as “aspect ratio”) of predominantly >3:1 fibers. For platy materials, such as clay minerals or polymer/clay nanocomposites, the properties of the composite are strongly impacted by the morphology of the particle. For montmorillonite the aspect ratio (height to diameter of plate) is generally 1:150. In industry, this ratio is commonly expressed simply as an aspect ratio of 150. The aspect ratio of platy and acicular morphologies is one measure of the anisotropy of nanoparticles.
A trioctahedral member of the true mica group. The end-member formula is NaMg3AlSi3O10(OH)2 and it occurs most commonly as the 1M polytype. Aspidolite is rare and can occur in meta-evaporates, in chromite sequences of mafic/ultramafic layered intrusions, gabbraic xenoliths, and metapelites. In older literature, aspidolite is referred to as sodium phlogopite (a term now considered obsolete).
An obsolete term for muscovite.