An obsolete term for muscovite.
An obsolete term for muscovite.
A pedofeature forming segregated lumps of material with diverse composition (similar to cutans) as part of a soil groundmass. The non-planar shapes and more distinct outlines differentiate glaebules from cutans. Three common glaebules include mottles, nodules, and concretions.
– nodule : a glaebule that is irregular to nearly spherical, with a massive internal structure.
– concretion : a nodule-shaped glaebule showing an internal structure of concentric layers.
– mottle : poorly differentiated glaebules occurring as diffuse patches in the groundmass.
A chlorite-like mineral containing Na in seven-fold coordination located between the interlayer octahedral sheet and the 2:1 layer. The ideal chemical composition is Na(Mg,Al)6(Si3Al)O10(OH,O)8. Glagolevite was described by Krivovichev et al. (2004) in analogy to chlorite as a tri-trioctahedral chlorite with polytypes IIb-6, IIb-2 and IIb-4. The mineral occurs at the Kovdor Phlogopite quarry, Kovdor massif, Kola peninsula, Russia.
A solid with a degree of order intermediate to the highly ordered arrangement of atoms, molecules, or ions in a “crystalline” solid and the highly disordered arrangement as found in a “gas”. Most glasses are in a metastable state and can be described as a supercooled liquid, which lack a melting point. Rapid cooling from a molten state (e.g., magma, lava) may result in a glass and this commonly depends on the volatile content of the melt. Not all glasses are formed from a melt. Although most opal forms from silica-saturated fluid under near-surface conditions, a rare “non-crystalline opal” (e.g., opal-AN) forms by transport of silica via steam to cold surfaces.
An iron-rich dioctahedral mica that shows K deficiency and limited substitutions of Al in the tetrahedral sites. Glauconite is a series name (Rieder et al., 1998) with a generalized composition of K0.8R3+1.33R2+0.67(Al0.65Si3.87)O10(OH)2, where viR2+/(viR2+ + viR3+) >= 0.15, and viAl/(viAl + viFe3+) <= 0.5 and shows no compositional overlap with celadonite. Often interstratified with smectite as the mixed-layered mineral glauconite/smectite. When mixed with other minerals or when referring to morphological features, the term “glauconitic” is appropriate. The mode of origin is not a criterion for identification.
A glaze is a vitreous, watertight coating often used to seal porous ceramics, such as earthenware. Glazes are commonly made from clay mixed with a flux to lower the melting temperature, then applied to the green body and fired. Colorants, commonly iron, copper, or cobalt compounds, may be added, especially to color vases or tiles.
Cf., ceramic, earthenware, green body, tile
Symmetry involving reflection across a plane coupled with a translation of a/2, b/2 or c/2 parallel to an axis (a-glide, b-glide, or c-glide, respectively) or between two axes (n-glide with translations of a/2 + b/2, b/2 + c/2, or a/2 + c/2; d-glide or diamond glide with translations of a/4 + b/4, b/4 + c/4, or a/4 + c/4) or between three axes for tetragonal or isometric crystals with a translation component of a/4 + b/4 + c/4.
An obsolete term for illite.
See diaspore.
A poorly known, modulated 2:1 layer silicate (Guggenheim and Eggleton, 1987). Although superficially resembling chlorite, gonyerite has a two-layer structure with structurally different types of interstratified layers. Inverted tetrahedra occur between the 2:1 layer and linked to the what would be the brucite-like interlayer in an ideal chlorite. Samples of gonyerite are generally impure, although an analysis by Frondel (1955) reported an approximate composition of (Mn3.25Mg1.95Fe3+0.64)(Si3.75Fe3+0.17Al0.08)O10.2(OH)7.8 and is based on the assumption that gonyerite is a chlorite and all iron is ferric. Gonyerite occurs in low-grade metamorphic, silicate-rich manganese deposits, such as that at the Harstigen Mine, Pajsberg, Värmland, Sweden.