A poorly defined material, possibly muscovite and pyrophyllite.

A dioctahedral member of the true mica group. The ideal end-member formula is KFe³⁺(Mg, Fe²⁺)□Si₄O₁₀(OH)₂, where □ = vacancy. The typical range in composition is: ^viR²⁺/(^viR²⁺ + ^viR³⁺) ≥ 0.25, ^viAl/(^viAl + ^viFe³⁺) < 0.5, Mg/(Mg + ^viFe²⁺) > 0.5 (Rieder et al., 1998). Celadonite is commonly an alteration product of pyroxenes and other Fe,Mg minerals found in basalts either during low-grade metamorphism or hydrothermal activity.

The cell parameters define the edges of the smallest repeating parallelepiped of the atomic arrangement of a crystal. Values of the cell parameters are usually given as three scalar cell lengths (a, b, c) and three angles alpha (between b and c), beta (between a and c), and gamma (between a and b).
Cf., unit cell.

A Ba-dominated feldspar mineral, Ba(Si₂Al₂)O₈.
Cf., alkali feldspar, feldspar, plagioclase feldspar

A temperature scale based on a degree, ^oC, where the freezing point of pure water at one standard atmosphere is arbitrarily set at 0 and the boiling point at 100^oC. One Celsius degree equals one Kelvin. 0^oC equals 273.15 K.
Syn., centigrade
Cf., Fahrenheit, Kelvin

A solid binding agent between grains/particles of natural rocks (e.g., sandstones), soils, or synthetic construction materials (e.g., geopolymer, Portland cement, concrete).
Cf., binder

The process of forming the mineral matter that binds particles of a sedimentary rock together. The cementation process usually involves a chemical precipitate from solutions that may originate within the sediment or from outside the sediment body. The mineral matter is called “cement”. In general terms, the stiffness and strength of the sediment or soil is increased by the mineral matter. The mineral matter is often clay minerals, oxides, silica, carbonates, sulfides and others.

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