Symmetry involving a repetition of identical features about a point at the center of the object. Thus, any point in the object will have a corresponding point (to produce an inversion) repeated an equal distance from the object’s center along a line established by the original point and the center point of the object. Also known as an “inversion center”.
Cf., symmetry, mirror plane, rotation symmetry, rotoinversion

Alteration that occurs from a grain boundary inward or from internal fractures within a grain toward the center of the grain. Centripetal replacement is often recognized by texture, especially if alteration is incomplete.
Cf., alteromorph, peripheral replacement, pseudomorph

A fine-grained inorganic solid produced by mixing milled raw materials with appropriate amounts of water, molding or shaping to obtain a green body (weakly bound solid mass), which is dried at room temperature, and then fired at temperatures >800°C. Firing temperatures >1200°C or glazes may be used to reduce the porosity to obtain watertight ceramics (e.g., for vases). Different raw materials can be used, depending on the type of ceramic to be produced. Clay (e.g., kaolin, bentonite), with marl, loam, feldspar, quartz, and lime are used for silicate ceramics (e.g., for bricks, clinker, or porcelain). Oxides Al₂O₃, ZrO₂, TiO₂, and Al₂TiO₅ are used for oxide ceramics (e.g., in car tires to reduce the rolling resistance, in blast furnace construction), and carbides SiC, BN, B₄C, Si₃N₄, or WC are used for non-oxide ceramics for plain bearing and soot particle filter in cars). Besides chemical and mineralogical differences, ceramic is often classified based on its porosity, which is determined by firing temperature. The most porous earthenware, (e.g., for flower pots) is fired between 950 – 1100°C, stoneware (e.g., for bottles, vases, tableware), is less porous and is fired between 1100 – 1300°C, and porcelain (e.g., for fine tableware) is the least porous due to its high firing temperature up to 1400°C. Pottery is a more general term for ceramic material fired above 400°C. The word ceramic is derived from the Greek word “keramos”, which means burned clay.
Cf., brick, clay, clinker, earthenware, glaze, green body, porcelain

Equivalent to kerolite.
See kerolite

See zeolite.

A poorly defined material, possibly an illite pseudomorph after cordierite.

An obsolete term for muscovite.

Chalcedony is a rock term to describe a mixture of a fibrous [112̅ 0] variety of microcrystalline (length fast) quartz and moganite.
Cf., quartzine

An obsolete varietal term for stilpnomelane.

See birnessite.