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
In soil science, soil or sand dilation involves the volumetric expansion of a saturated clayey soil or sand body when subject to drained shearing. For a stiff, highly over consolidated saturated clayey soil subject to drained shearing, pore water may generate a negative pressure and water external to the body tends to flow into the soil (or sand), and hence its total volume increases, indicative of dilation behavior.
Cf., contraction, soil or sand;
A species of the chlorite mineral group with dioctahedral sheets only (e.g., donbassite)
Cf., trioctahedral chlorite, di,trioctahedral chlorite, dioctahedral sheet
In the ideal case, the smallest structural unit in a phyllosilicate contains three octahedra. If two such sites are occupied with cations and one site is vacant, then the octahedral sheet is considered “dioctahedral”. If all three sites are occupied, the sheet is considered “trioctahedral”. (Quot Guggenheim et al., 2006; see also references therein). A dioctahedral sheet generally contains predominantly trivalent cations.
Cf., trioctahedral sheet
A clinopyroxene with an end-member composition of CaMgSi2O6. A continuous solid-solution series exists between diopside and hedenbergite, CaFeSi2O6. Diopside occurs in metamorphic rocks, alkali basalts, and nodules in kimberlite. Near end-member diopside occurs in metasomatic rocks, such as skarns formed through contact metamorphism between siliceous carbonate and granitic intrusion.
See pyroxene group for additional details
An obsolete term for margarite.
A measure of the unequal distribution of negative (electrons) and positive (protons) charge in an atom, molecule, or solid, with units of charge times distance (1 Debye, 1 D = 3.335641*10-30 C.m = 10-10esu, where esu = electrostatic valency units). A molecule has a nonzero dipole moment if the individual bond dipole vectors do not cancel (e.g., a water molecule).
Cf., polarization
Not a valid term, previously used as a classification of the micas where the number of silicon atoms per formula unit is two per four tetrahedral sites, see Rieder et al. (1998).
Cf., mica, true mica, brittle mica, interlayer-deficient mica, group names