Describes a property of material where there is repulsion by a magnet.
Cf., magnetic susceptibility, magnetism
Describes a property of material where there is repulsion by a magnet.
Cf., magnetic susceptibility, magnetism
A polymorph of hydrous aluminum oxide, alpha-AlO(OH), and isostructural with goethite, alpha-FeO(OH). The structure is comprised of double chains of edge-sharing octahedra of AlO3(OH)3along the c axis, and the chains are offset along the b axis. Diaspore occurs with corundum, often in chlorite schists and in dolomite, and as a major constituent as fine-grained matrix in bauxite.
A soft, naturally occurring, sedimentary rock, of marine or freshwater origin, composed of biogenic silica derived from tests (shells) of single-celled algea (diatoms). Diatomaceous earth has a high melting point (1715oC) and is used in filters, mild abrasives, thermal insulators, and absorbants.
Syn., diatomite
A member of the kaolin group, which consists of the dioctahedral and aluminous rich 1:1 phyllosilicates. Dickite has a chemical composition of Al2Si2O5(OH)4. Dickite is distinguished from the other polymorphs, kaolinite and nacrite, by the vacant octahedral site regularly alternating from layer to layer across “B” and “C” sites. Thus, the polytype is a two layer formwith monoclinic symmetry, Cc. The “B” and “C” sites would be related by a mirror plane if both sites were occupied identically within the same layer, whereas the “A” site resides on the mirror plane (Bish and Johnston, 1993). Dickite has a widespread occurrence and often is believed to be transformed from kaolinite (and therefore dickite is the more stable phase) by higher temperature (various temperatures have been suggested depending on origin, e.g., ~120oC, 290 – 300oC, 80 – 160oC), but dissolution-precipitation of kaolinite to dickite has been suggested also, as well as direct precipitation. Dickite has been described from hydrothermal and diagenetic environments. Examples of hydrothermal dickite include those of Japan and Nayarit, Mexico.
Cf., halloysite, kaolin, kaolinite, nacrite
An obsolete term for muscovite.
An obsolete term for muscovite.
All surface charges are balanced by oppositely charged counter ions. Some of these counter ions are bound, usually transiently (see cation exchange), in the so-called Stern or Helmholtz layer, some of them may diffuse away from the surface and form a diffuse layer. Both the charged surface and the diffuse ions form the electric double layer, which in total is uncharged. The thickness of the diffuse layer is solely a function of the ionic strength of the solution. The distance 1/kappa, where the thickness has decreased to roughly 1/e is called the Debye (screening) length. The thickness decreases with increasing ionic strength because of the screening effect of ions.
Cf., Stern layer
The process of mass transfer of matter from areas of high activity to low activity, or of energy where heat is transferred from higher temperatures to regions of lower temperature, over time. Diffusion is generally driven by thermal vibration of the mass.
The temperature dependent process of mass transfer of matter in solids from areas of high concentration to low concentration. Volume diffusion commonly occurs along interstitial channels or grain boundaries, or by vacancy exchange with an atom, ion, or molecule.
See diffusion.
a) a property of a non-Newtonian fluid where the viscosity of the fluid increases sharply at high shear rates but is constant for constant shear rates. The viscosity is reduced again if not agitated (e.g., stirred).
Cf., Newtonian fluid, quick clay, thixotropy, rheopexy
b) In soil mechanics, dilatancy refers to the volumetric increase (i.e., dilation) behavior or property of a clay subject to drained shearing at or near the peak shear stress. A dense soil (e.g., dense sand, overconsolidated clay) exhibits volume expansion (i.e., the soil takes water into its void space) if sheared with drainage allowed, or reduced porewater pressure (i.e., a tendency for volume expansion or dilation) if sheared without drainage allowed. Usually maximum dilation rate corresponds to the peak shear stress or failure strength.
Cf., drained shear, undrained shear; dilation; contraction