A discredited term for a Si- and Fe-rich (clinochlore) chlorite.

The chemical, physical, and biological reactions incurred by sediment during burial, after initial accumulation. Diagenesis reactions may involve addition and removal of material, transformation by dissolution and recrystallization or replacement (authigenesis), or both, and phase changes (See Ostwald ripening). Weathering, incurred by sediments at the Earth’s surface under ambient conditions, is not part of the diagenesis process and represents the lower temperature limit of diagenesis. Hydrothermal, geothermal, and contact metamorphism are not considered part of the diagenesis process. The lowest grade of metamorphism limits the diagenesis process at high temperature and high pressure. In clay-rich rocks, the boundary between diagenesis and very low-grade metamorphism (anchizone is the transitional zone) has a Kübler index of 0.42 – 0.25 degrees two theta. Reduction of smectite interlayers in illite-smectite interstratifications to <10% is typical of the diagenetic zone-anchizone transformation (Merriman and Peacor, 1999). Weaver and Brockstra (1984) proposed a boundary between diagenesis and metamorphism as that point at which disordered illite (1Md) has been converted to ordered (1M, 3T or 2M1). “Retrograde” diagenesis was described by Nieto et al. (2005) as “fluid-mediated retrograde processes occurring under diagenetic conditions”. See anchizone, epizone, interstratification, Ostwald ripening, smectite-illite
Cf., Kübler index

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 (1715^oC) and is used in filters, mild abrasives, thermal insulators, and absorbants.
Syn., diatomite

See diatomaceous earth.

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., ~120^oC, 290 – 300^oC, 80 – 160^oC), 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.

See insulator.