a hard, compact aggregate of mineral matter in sedimentary or pyroclastic igneous rocks (ash or cinders), subspherical to irregular in shape, formed by precipitation from water solution, usually around some nucleus, such as a small chunk of shell or bone. Concretions generally are different in composition from the rock in which they occur and represent a concentration of some minor con-stituent in that rock.
(a) A hard, compact mass or aggregate of mineral matter, normally subspherical, but commonly oblate, disk-shaped, or irregular with odd or fantastic outlines; formed by precipitation from aqueous solution about a nucleus or center, such as a leaf, shell, bone, or fossil, in the pores of a sedimentary or fragmental volcanic rock, and usually of a composition widely different from that of the rock in which it is found and from which it is rather sharply separated. It represents a concentration of some minor constituent of the enclosing rock or cementing material, such as silica (chert), calcite, delimite, iron oxide, pyrite, or gypsum, and it ranges in size from a small pellet-like object to a great spheroidal body as much as 3 m in diameter. Most concretions were formed during diagenesis, and many (especially in limestone and shale) shortly after sediment deposition. (b) A collective term applied loosely to various primary and secondary mineral segregations of diverse origin, including irregular nodules , spherulities, crystalline aggregates, geodes, septaria, and related bodies.
A local concentration of chemical compounds (e.g. calcium carbonate, iron oxide) in the form of a grain or nodule of varying size, shape, hardness, and color. Concretions of significance in hydric soils are usually iron and/or manganese oxides occurring at or near the soil surface, which develop under conditions of prolonged soil saturation.
Concretion - A hard rock, usually imperfectly round, formed by precipitation from water in the pores of another rock and usually varying greatly in composition from that of the rock in which it occurs.
A hard round, oval, or other-shaped of mass of mineral or aggregate matter of varying sizes. Commonly forms by chemical precipitation around a nucleus or center, or replacement of precursor organic or inorganic material. An example is siderite (iron, calcium carbonate) concretions.
A bulbous mineral concretion usually found within a layer of sedimentary rock. Often called Turtle Stones. They are formed by minerals found within rock layer precipitating towards a nucleus (mineral or bone) and under great pressure, form a rock, harder than the surrounding rock.
Stone-like encrusted clump/conglomerate created by the natural elements around an artefact, often rusted iron. If a concretion around an iron object is cracked underwater, black "smoke" pours out. This is not good, because without the protective concretion, the remaining iron is exposed to further rusting. Concretions should never be cracked, just documented. If a decision is made to recover, the entire concretion should be recovered and quickly be placed in a jar of sweetwater, pending further investigation, possibly by X-ray. A concretion sometimes contains the hollow space after an object that has rusted away. Thus it's important not to crack it. Such a hollow can be casted by filling it with epoxy, saving the object's original form.
a nodular or irregular concentration of certain authigenic constituents of sedimentary rocks and tuffs developed by the localized deposition of material from solution, generally about a central nucleus are solid, grow from the center outward & are generally noncrstalline though some crystals have been observed concretions are formed by the deposition of distinct minerals, different from the surrounding rock, very firmly cemented around a nucleus most common cementing materials are calcite, siderite & silica parts of plants, animals & well-preserved fossils may be found at the nucleus harder than enclosing rock
(con-cre´-tion) A hard, compact aggregate of mineral matter, subspherical to irregular in shape, formed by precipitation from water solution around a nucleus, such as a shell or bone, in a sedimentary or pyroclastic rock. Concretions are generally different in composition from the rock in which they occur and represent a concentration of some minor constituent of that rock. Chert, iron oxide, and pyrite are among the common materials that form conretions.
n. A hard, rounded mass, commonly of silica, calcite, dolomite, iron oxide, pyrite, or gypsum, that formed within a rock from the precipitation of these minerals around a nucleus, such as a leaf, bone, shell, or fossil, and ranging in diameter from centimeters to meters.
A concretion is a volume of sedimentary rock in which a mineral cement fills the porosity (i.e. the spaces between the sediment grains). Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin con meaning 'together' and cresco meaning 'to grow'.