concretion


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concretion,

mass or nodule of mineral matter, usually oval or nearly spherical in shape, and occurring in sedimentary rock. It is formed by the accumulation of mineral matter in the pore spaces of the sediment, usually around a fossil or fossil fragment acting as a nucleus. Most concretions are very dense and compact, and are usually composed of calcite, silica, or iron oxide. The material making up the concretion is believed to come from the surrounding rock, being redeposited around the nucleus. Concretions range in diameter from a fraction of an inch to many feet, although most are but a few inches in diameter. Perhaps the best known are the flint nodules found in chalk deposits such as those at Dover, England. Concretions having radiating cracks filled with mineral matter are called turtle stones, or septaria.

concretion

[kän′krē·shən]
(geology)
A hard, compact mass of mineral matter in the pores of sedimentary or fragmental volcanic rock; represents a concentration of a minor constituent of the enclosing rock or of cementing material.

concretion

1. any of various rounded or irregular mineral masses formed by chemical precipitation around a nucleus, such as a bone or shell, that is different in composition from the sedimentary rock that surrounds it
2. Pathol another word for calculus
References in periodicals archive ?
As shown in Figure 10, when the vibration duration increases from 20 s to 140 s, the grouting diffusion rate and the concretion volume increase rapidly at the early stage.
(i) In scheme I, there are 4 groups to test the shear strength of pure cement grout concretion under different water cement ratio.
In adult statoliths of Bolinopsis and Pleurobrachia, the hard concretion filling the vacuole is displaced during sectioning, leaving a large hole, but not if tissue is treated with EGTA or EDTA during fixation (Tamm, 1982).
The roundness of concretions, different lithology from the host sediment, and the soft deformation structures in the underlying sediments suggest the reworking origin of these concretions.
As concretion comes away, the revealed wood and metal must be chemically treated to avoid further corrosion.
Some concretions constantly are sprayed with water to preserve the artifacts within; others rest inside water tanks.
These layers thicken over time, forming dense, concrete-like shells called "concretions." Concretions are a mixed blessing for maritime archeologists: Although they can help preserve the artifacts they encase, they also conceal their contents.
The intrinsic concretion of the idea constitutes its latent actuality, which necessarily becomes manifest in the finite and the temporal as the intelligible power of the self or as the powerful intelligibility of facts.
The charity even has an intensive course on how to deal with dust, which enables staff and volunteers to compare strategies and share any problems they may have if they should be unfortunate enough to discover concretion (that age-old problem of when humidity turns dust into grey liquid matter).
How in each case can the right combination of firm rootage and openness, of concretion and universalism, be found?
Isabel Archer and Maisie are versions of the woman of genius; but Maisie, Matz shows, 'is the best proof that for James, impressions, despite their reputation, are abstractions, but abstractions which require the simplicity we associate with (and figure as) concretion' (p.