concretion
[kɔ̃kresjɔ̃]
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f.
凝结，凝固，固化；凝结物；〈医〉结石；〈地〉结核
Concretion
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abstract:
A concretion is a hard, compact mass of sedimentary rock formed by the precipitation of mineral cement within the spaces between the sediment grains. Concretions are often ovoid or spherical in shape, although irregular shapes also occur.
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WordNet